For your first bike, Speed shouldn't even enter the equation. Stability, rideability, and crash survivability should be the factors.
As far as beginner bikes go, The ZX-7R is probably a little big, but much more stable and easier to ride then late model bikes. It is very stable, and very stout. You can throw a 7R down the road quite a few times before it is done. An R6 can be totalled falling off the kickstand (seen it happen).
Sure, it weighs more, but that extra weight makes it very stable once your moving.
Next race season, I plan on finding out if the 7R can still be competitive. I haven't weighed mine yet, but I'm sure I've pulled 60 pounds or so off of that bike. The kickstand weighs about 4 pounds. The headlights weigh about 15 pounds. Stock bodywork is WAY heavy. I hope to have pics of the newly painted bike up soon... when the paint job is done.