Serve: Fed vs Grosjean

I stumbled across this photo of some player (turned out to be Grosjean) and wondered what looked different from Federer. Couple things I can see:

• Fed's head is farther back, chin towards the ball, Grosjean's is leaning into the shoulder
• Fed's tossing arm and racket form a triangle, Grosjean's diverge
• Fed's wrist is pronated a bit more
• Fed's racket is closer to his head
• Fed's tossing arm is relaxed and slightly bent