I find that if I don't skip my upper body workouts, lifting a few extra cork rings (and their associated adhesive) becomes almost doable, but if you add the weight of sealer on the other hand, I'm only good for maybe 8 reps.....
Seriously though, split grips are popular because they look cool (in addition to saving $ on cork). The only issue with split grips is that if the dimensions of the handle are less than ideal, one ends up griping bare blank. I have a few stock split grips, but prefer full handles. My customs are mostly split grips. Like most other things, it comes down to preference, and what works for each angler.