I have 600X CF cards and 600X SDHC for my 5D. In my Rebel T2i I use Panasonic Class 10 cards. The Rebel can write about 20 minutes of movie, continuously, and it can take 6 or 7 raw files in a burst and then be ready for another burst a second later.
I agree with Stef. I have Bowens strobes. Single shot is the way to go regardless of body or card, because if you take a two shot burst the second shot will be black, the strobes have not recovered. If I use hot lights or speedlights, I can shoot faster but still, what’s the point, the model is just sitting/standing there. Portraits and weddings are much slower paced than sports and wildlife.
I shoot all sorts of things and have never felt I needed the Rebel with class 10 cards to be faster. That said, the new 5D has much better auto-focus so for shooting sports and some animals it is a better choice. It also takes bigger, cleaner images, but it is about seven times the dollars. For about twice as much again there is the 1Dx, which is also pretty impressive.