I have gone through a half dozen or so old Makita's, a half dozen Hitachi's, a half dozen old dewalts, (all of them ni cad of various voltages) and now have a dozen or so dewalt 20 volt li ion. several impact drivers, several drills, and a couple oddball tools. The lithium ion batteries are great- they can be stored charged for a long time and not lose the charge. Never had a problem with any of them, they are in daily service. I keep them with dedicated bits and drills in them, so as to not have to change them. Have not had a battery pack go bad yet, which is a big change from ni-cad.
IMO, Any of the new lithium ion brand name tools are going to be OK- the competition in cordless tools is intense. I really doubt any normal use will show a big favorite- of course, I am coming from an era when Milwaukee's cordless drill had a cord, and a 12 volt belt mounted battery.....
I would put ergonomics first- does the tool fit your hand? And shop the sales- sometimes you can buy two tools, two battery packs and a charger for the cost of two spare batterys...crazy.
and the most important part- buy good driver bits, and lots of them, and long enough so your fingers don't take a beating.