Assume Splinter@10 is cast on the recharge and always scores every trigger on every hit. It's maximum possible DPS is (4*35*3)/6 = 70.
Splinter@16 has a maximum possible DPS of (5*53*3)/6 = 132.5.
Both of those figures are maximum possible values that are rather unrealistic. You're not going to get 3 adjacent foes on all 5 hits every time you cast Splinter. In fact, you're probably going to get a lot less. Each missed trigger takes ~9DPS off the r16 Splinter's maximum.
By comparison, assume GDW@10 is cast on the recharge, and your team has enough sins to put it on, and they are using JS+FF+DB+auto+auto. Your DPS would be (20 / 6) * 20 * 1.86267039 = 124.178026.
And that is a pretty realistic number because the sins are going to keep swinging.
If r16 Splinter misses a trigger or two per cast (quite likely), it's going to have less DPS than GDW.
Splinter's only serious advantage is that it can be spikey when combined with multi-hit attacks.
Then there's GDW's really, really powerful KD effect to consider.