Good analysis, I agree excluding two points:
- Cilic hits dropshots
- Cilic has more variety than other two
I've seen Cilic use the drop shot quite a bit in matches, he definitely uses it, not a dramatic amount, but more than Del Potro. Obviously not on the same level as Gulbis, though.
Cilic definitely has more variety since he comes to net more, slices the backhand more, can hit slice or kick or flatten serves, can play more or less offensive depending on the opponent and how he is playing etc. Gulbis has a little bit of variety, and Del Potro has one basic style of play.