I had a snapon ct1440 (14.4v 3/8 drive) for 3 years. Was very happy with its power and durability.
Well, the brushes went out in the motor a few months ago and I made the switch to Milwaukee m18 3/8. I made the switch mainly because I was planning to expand my cordless collection and didnt want 15 chargers. I felt that Milwaukee had one of the best selections of tools and were always near the top for power.
Overall I am very happy with the Milwaukee. I think build quality is equal to my old Snap-On and the lithium batteries are a plus. The Snap-On hits slightly harder. But in using the Milwaukee for the last few months literally everyday (I'm a forklift/construction equipment technician), I've come across maybe 2 bolts that the Snap-On could get off that the Milwaukee couldnt, and the Snap-On still had to hammer for a little while before they broke loose (2 co-workers just bought ct1440's and I was able to test them back to back on the same fastener). It feels like the Snap-On hits slightly harder (maybe a different hammer?). But it also weighs more, is larger in size, and doesnt have lithium batteries.
For me the slight decrease in power was worth the additional tools available for a lot less money that utilize the same battery.
I also like that the Milwaukee's LED light stays on for 10 seconds after the trigger is pulled, then fades off. Something that seems to be a recent addition from Milwaukee as older ones didn't stay on and would require the trigger to be pulled slightly to turn on.
Milwaukee also recently came out with brushless drills and a 1/4 hex impact driver. I was hesitant to buy my 3/8 because they'll probably come out with a brushless 3/8 impact soon but after having a cordless impact for so long, I couldnt sit around waiting
