Just a personal preference.
How big are your hands ?
How much bar end do you mind rising above your grips ?

My wife likes the smaller ones on her commuter, guess it is the gp3. She has smaller hands and wants less intrusive bar ends.
I run smaller bar ends on my flat bar hybrid/roadie bike than I like on my converted mtn commuter (biggest I could find then covered in old tube then grip tape) or steel monster cross commuter.

Another factor is:
How long are your rides/commutes ?
Longer I am on the bike, the more important multiple hand position becomes......
Then trekking bars, drops, or Jones H style makes more sense.