The catch
Brother MFC-L3720CDW
It cannot scan both sides automatically and has no wired Ethernet connection.
Side by side
Brother MFC-L3720CDW vs MFC-L3780CDW: No second pass needed, 3780 scans both sides
Quick verdict
Double-sided originals, Ethernet or regular mixed-media jobs make the MFC-L3780CDW the better buy. A Wi-Fi office that scans mostly single-sided pages and does not need fast color batches is well served by the MFC-L3720CDW.
Before you buy
Why, and what it costs you
Different amounts of work can hide behind the same fifty sheets
There are 100 faces in a 50-sheet two-sided packet. The 3780 captures both faces in one pass. For the backs, the 3720 needs a separate workflow even though its feeder capacity is the same.
Where this comes from
50 sheets x 2 faces=100 faces. Both ADFs hold 50, only the 3780 scans single pass.
The catch
Brother MFC-L3780CDW
Compared with the main cassette, the 30-sheet multipurpose tray is small.
Brother MFC-L3720CDW
- Why pick it
- The forms you scan are one-sided
- Your shared printer can live on Wi-Fi alone
- The catch
- It cannot scan both sides automatically and has no wired Ethernet connection.
Brother MFC-L3780CDW
- Why pick it
- Regular scanning of both document sides
- Ethernet and a multipurpose tray are on your list
- The catch
- Compared with the main cassette, the 30-sheet multipurpose tray is small.
We may earn a commission from qualifying Amazon purchases. How we make money
What this page compares
Two-sided scanning, Ethernet and special-media loading are where these machines part ways. The MFC-L3780CDW changes more than how fast color pages come out.
Double-sided originals, Ethernet or regular mixed-media jobs make the MFC-L3780CDW the better buy. A Wi-Fi office that scans mostly single-sided pages and does not need fast color batches is well served by the MFC-L3720CDW.
Which one fits
Pick the situations that sound like you
Contracts from several coworkers, printed two-sided
Single-pass scanning means the stack never has to be returned by hand.
- Brother MFC-L3720CDW
- Caution
- Brother MFC-L3780CDW
- Better fit
School handouts printed on one side, plus color copies now and then
A 50-sheet ADF and a flatbed come on each.
- Brother MFC-L3720CDW
- Good
- Brother MFC-L3780CDW
- Good
Ethernet is required by office policy
The 3780 alone has the wired port.
- Brother MFC-L3720CDW
- Not suitable
- Brother MFC-L3780CDW
- Better fit
Brief runs using a second supported paper stock
Repeated loading is cut down by a 30-sheet multipurpose tray.
- Brother MFC-L3720CDW
- Caution
- Brother MFC-L3780CDW
- Better fit
In practice
Differences you will notice
Different amounts of work can hide behind the same fifty sheets
There are 100 faces in a 50-sheet two-sided packet. The 3780 captures both faces in one pass. For the backs, the 3720 needs a separate workflow even though its feeder capacity is the same.
How we worked this out
50 sheets x 2 faces=100 faces. Both ADFs hold 50, only the 3780 scans single pass.
A bypass tray earns its keep on a day with mixed paper
A 250-sheet main cassette and a 30-sheet multipurpose tray come together on the 3780. You can leave ordinary paper loaded and feed a supported alternate stock as a batch, rather than loading one sheet over and over.
How we worked this out
3780 paper input is 250+30, 3720 is 250+1. Media still follows the manual.
Better Wi-Fi cannot supply scan hardware that is missing
Documents can be shared over Wi-Fi from the 3720, yet neither faster networking nor a software setting makes its simplex ADF into the 3780 single-pass scanner.
How we worked this out
Duplex scan: No on 3720, Yes on 3780 single pass.
Option A
Brother, MFC-L3720CDW
MFC-L3720CDW
A Wi-Fi office that copies in color and scans stacks of single-sided documents.
- Best for
- The forms you scan are one-sided
Facts we checked
- Scanning both sides: Handled manually
- Ethernet: No
- Color speed on Letter: Up to 19 ppm
- Special-media input: A manual feed for one sheet
Option B
Brother, MFC-L3780CDW
MFC-L3780CDW
Color charts and two-sided paperwork for a shared network.
- Best for
- Regular scanning of both document sides
Facts we checked
- Scanning both sides: Automatic, in a single pass
- Ethernet: Gigabit speed
- Color speed on Letter: Up to 31 ppm
- Special-media input: Multipurpose tray of 30-sheet capacity
Spec by spec
Where they really differ
| Spec | Brother MFC-L3720CDW | Brother MFC-L3780CDW | In practice |
|---|---|---|---|
| Scanning both sides | Manual handling | Single-pass automatic | For supported two-sided originals, the 3780 does away with the return pass. |
| Ethernet | No | Gigabit Ethernet | If the office connection must be wired, the 3720 is out. |
| Letter color speed | Up to 19 ppm | Up to 31 ppm | The extra throughput is worth more on longer color runs. |
| Special-media input | One-sheet manual feed | 30-sheet multipurpose tray | Supported media needs less individual loading on the 3780. |
| Document feeder | 50 sheets | 50 sheets | The sheet count they accept is the same, but the number of faces they capture automatically is not. |
Trade-offs
What each pick costs you
With Brother MFC-L3720CDW
- When you switch back and forth between larger batches of paper stock, its one-sheet manual feed is a limitation.
With Brother MFC-L3780CDW
- A scan packet that goes above 50 suitable sheets has to be fed in more than one load.
Change of plan
When the answer changes
Both sides are often printed on the paperwork that comes in
Go with Brother MFC-L3780CDW. The real bottleneck is what the duplex scanner deals with.
Your originals have a single side printed, and Wi-Fi is enough
Go with Brother MFC-L3720CDW. If the saving is worth it, the 3720 handles that workflow.
You need a 50-sheet special-stock batch to run unattended
Neither model fits. The 3780 multipurpose tray fits only 30 sheets. It does not take 50. Media weight limits need checking as well.
Decision guide
How to decide
If you deal with double-sided originals, need Ethernet or regularly mix media types, choose the MFC-L3780CDW. The MFC-L3720CDW fits a Wi-Fi office that mostly scans single-sided pages and has less need for fast color batches.
The biggest gap is in incoming documents
Automatic two-sided printing comes with each. The upgrade that tends to pay off is on the input side, because the 3780 captures double-sided forms with no extra manual pass.
Feeder capacity and scan speed are different things
With both feeders taking 50 sheets, the scanner specs can look alike at a glance. Capturing faces and counting passes are separate matters, though. For an archive of two-sided forms the 3780 is the strong favorite, before print speed even comes up.
Switching media gets easier with a mixed-media tray
An office that switches between plain reports and supported letterhead or heavier stock gets a practical benefit from the 3780 multipurpose tray. You still need the right media setting and paper that is supported, and a capacity figure does not mean any label or envelope will work.
Skip features for a workflow you lack
A household that prints short color jobs and now and then scans a one-sided sheet may be fine with the 3720. Toner plus separate maintenance consumables apply to both, so go through the full supply list before you decide either one runs cheaper.
What this page can’t tell you
- Manufacturers supply the rated print speeds. Matched hands-on tests were not done.
- Standardized test documents produce toner yields, and actual content varies.
By the numbers
What the data shows
What we found across the laser printers we compare, plus the checked facts behind each finding.
Show the facts and the math
| Product | Needs it meets | Facts we checked | Sources |
|---|---|---|---|
| Brother MFC-L3720CDW |
|
| |
| Brother MFC-L3780CDW |
|
|
Ready to buy
See today’s price and what owners say
Open either model on Amazon for the current price, customer reviews and delivery options.
Brother MFC-L3720CDW
The forms you scan are one-sided
See price & reviews on AmazonBrother MFC-L3780CDW
Regular scanning of both document sides
See price & reviews on AmazonEach link opens in a new tab.
We may earn a commission from qualifying Amazon purchases. How we make money