I talked to my snap on guy the ohter day about this because I am buying an mg725 impact and was seeing what he could do about the pricing because of the flier and he said a big reason they get it that cheap is because its for big accounts like the military who buy all the tools for their...
I recently bought the m18 fuel 3/8 impact and absolutely love it. SInce it seems like you want to stay compact I would really suggest getting the 3/8 version. I have had a 1/2 milwaukee impact (the 450 ft/lbs one) and did an entire engine swap in my home garage only using that and it never gave...
For light work I would suggest a 3/8" because they are usually lighter weight. But that is only if you don't need more torque than a 3/8 is capable of. Another way to put it is if on average you are dealing with much more bolts around 14 mm and below go with a 3/8 but if you are dealing more...