I started with the PC BN125 (18 ga. brad). Worked great on base shoe
and quarter round floor trim.
Two of my friends have the PC FN250 (16 ga. finish) which I can
borrow, so I went with the PC DA250 (15 ga. angle finish). Did a nice
job on the garage door trim, though it's a large unit.
Some trim which I have removed is installed with narrow-crown staples,
so I picked up a Spotnails WS4840 at the local framing supplier. It's
not the smallest, but it holds many staples before needing a reload.
Put up some fascia outside trim on a carport and a church with it.
Light, quiet and easy to use at arm's length.

You will eventually find a use for all 3 as stated before.