What's inside
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Quick verdict
For a drill that has to fit between cabinets, inside a vehicle, or behind plumbing, the Bosch PS31 is the smaller, lighter choice. Its head is about 6.5 inches long and the tool weighs roughly 2.1 pounds with a compact battery. That short nose and low weight matter more than extra power when you’re repeatedly reaching into awkward spaces.
The Milwaukee M12 Fuel 3403 is the stronger, more capable all-rounder. It is a brushless drill with a 1/2-inch chuck, while the PS31 is a brushed drill with a 3/8-inch chuck. Choose the Milwaukee if you expect larger holes, heavier fastening, or want a drill that can take a wider range of bits. It is not the better fit in every tight spot: its longer head can make the difference between reaching a fastener and having to move the workpiece.
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At-a-glance comparison
| Feature | Bosch PS31 | Milwaukee M12 Fuel 3403 |
|---|---|---|
| Chuck | 3/8-inch keyless | 1/2-inch keyless |
| Motor | Brushed | Brushless |
| Maximum speed | Up to 1,300 rpm | Up to 1,550 rpm |
| Clutch | 20 settings plus drill mode | 16 settings plus drill mode |
| Length | About 6.5 inches | About 5.8 inches, depending on measurement point and configuration |
| Typical bare-tool weight | About 1.8 pounds | About 1.7 pounds |
| Best fit | Short reach, light fastening, small holes | More demanding drilling and a larger bit range |
Published dimensions and weights can vary by battery, measurement method, and kit. Check the exact tool listing if a fraction of an inch or a few ounces will determine whether it fits your space.
Which one fits tight spaces better?
The PS31’s main advantage is its compact nose. At around 6.5 inches long, it is easy to steer between framing, inside drawers, or under a sink. Its 3/8-inch chuck also keeps the front end relatively compact. For installing cabinet hardware, assembling furniture, or driving small screws where access is poor, it is an easy tool to control.
The 3403 is shorter on published dimensions, but its larger 1/2-inch chuck and head shape mean length alone does not settle the question. Check the clearance around the chuck and bit, not just the bare tool. A long bit or a right-angle obstruction can eat up the space advantage of either drill. If your problem is a corner the drill cannot physically enter, a 12V right-angle drill may be a better solution than choosing between these two straight drills.
Neither model turns a drill into a solution for every confined space. If the chuck cannot line up squarely with the screw, you risk stripping the head or walking the bit across the surface. A short bit holder, stubby driver bit, or a proper right-angle attachment may help, but attachments add length and can flex under load.
Power, control, and likely failure points
The 3403’s brushless motor and higher speed give it more headroom for regular drilling. Its 1/2-inch chuck accepts larger-shank bits than the Bosch’s 3/8-inch chuck, and that makes the Milwaukee more versatile for hole saw arbors and larger drill bits. It is the safer pick if this will be your only 12V drill and your jobs vary.
The PS31 is not a heavy-duty drill, but that is not a drawback for its intended work. It handles pilot holes, small twist bits, and ordinary fasteners well. Its 20 clutch settings make it straightforward to reduce torque on small screws. Set the clutch too high and a compact drill can still snap a screw, strip a soft screw head, or spin a small workpiece. Start low, then increase the setting until the fastener seats cleanly.
For large holes in thick lumber, repeated hole-saw work, or long screws into dense material, neither compact 12V drill is the ideal substitute for a full-size drill. The 3403 has more capacity, but forcing a small drill can overheat the motor, drain a compact battery quickly, or stall the bit. Use a sharp bit, clear chips from deep holes, and back off if the tool slows sharply. For frequent heavy drilling, consider a brushless 18V drill driver instead.
Battery platform and value
These are platform purchases as much as tool purchases. A bare tool is a bargain only if you already own compatible batteries and a charger. Compare the full kit price, battery capacity, and charger before choosing; a small compact battery keeps either drill light but will run down sooner during repeated drilling than a larger pack.
The Bosch is the sensible buy when tight access and light fastening describe most of your work, especially if you already own Bosch 12V batteries. It is also a reasonable lower-cost option for occasional home repairs. The Milwaukee earns its price when you need the 1/2-inch chuck, brushless motor, or broader drilling capacity and already use M12 tools. If you are starting from scratch, compare complete kits rather than assuming one bare tool is cheaper overall.
What to buy
Buy the Bosch PS31 if your priority is a compact, light drill for cabinets, furniture, service work, and small fasteners. Its narrower chuck and brushed motor limit heavy-duty use, but for those jobs they are fair trade-offs for easy handling.
Buy the Milwaukee M12 Fuel 3403 if you want more drilling range, a 1/2-inch chuck, and a brushless motor in a small platform. It is the stronger general-purpose choice, though it may not reach where the Bosch’s narrower front end does. Before ordering either one, measure the tightest clearance and include the bit length; that simple check can prevent buying a drill that still will not fit the job.