I used to do tossing arm first, but I found a better rhythm with racket arm first (which sort of came together with a more comfortable weight shift timing).
I'd prefer to have a slightly lower toss (cause I hate the wind and have a terrible toss to begin with).
Sampras was toss first. I feel like Roddick is either toss first or unison (because of abbreviated motion). Nadal seems pretty toss first. Federer might've been toss first pre-2003... I'm not sure... But now he's racket arm first.
If you look at it in extreme detail though, they are all basically in unison (just that the "lagging" arm is moving relatively slowly). There are very few people with defined, separate motions for their toss and takeback.
And it's all personal preference. I did toss first because I couldn't conceive the idea of starting the takeback a little before my toss without doing an abbreviated or separated motion, because I was taught to bring both up at once. Now I do takeback first because, like I said, it's a better rhythm for me and it incorporates better weight shifting.
[K]Six.One Tour (3) 367.5 grams 31.7 cm balance.
Mains: Babolat/Wilson Natural Gut @ 23 kg // Crosses: Luxilon Alu Power Rough @ 21.5 kg