Of these two choices, either one is acceptable IMO (If you have the judgement for riding on public roads in the first place...), the 650 is the better starter bike. It is much more user-friendly, and it's a great bike. I have one and I just sold my ZZR about 2 months ago when I finally got my ZX14.
The 650 is a great all-around bike, and it's plenty easy to start out on, if you are at least 5'6", or so, and have the aforementioned judgement. I also have a Ninja 250 (My wife rides our bikes, as well.). It's a great bike, too, but I think you'd want more in pretty short order, unless you're a very moderate, conservative, strictly practical rider.
Go w/the 650. It's the best compromise of starter/do-anything-you-want- for-a-long-time bike. If you're a typical 20 year old enthusiast, you're going to want more too soon, anyway. It's a disease. Just keep it in check, so as not to kill yourself.