Everyone above is right. You didn't really mention if this is your first bike. If you already have some experience, like with dirtbikes for example, I suspect you'll be more happy on a 400cc or 500cc bike. The CBR500 gets a bad rap for some reason but complaints seem to come from seasoned riders. But for a big guy learning how to ride, I think this is probably appropriate. When you start getting into the 4 cylinder bikes (generally sport bikes 600cc's and up), then those are more for intermediate riders. 1 or 2 cylinder bikes are generally docile and can be driven by any beginner, assuming the bike is light enough that you can lean it over without dropping it and with a seat short enough to touch the ground. You can find the "wet" weight of any vehicle online. A Suzuki SV650 has a wet weight of about 430lbs, and the CBR250r is about 370lbs. You're a big guy. If you have the strength to hold up the extra 60lbs, you'll get more out of the the 650cc bike.
My opinion only, but...
Pros of a 250cc bike:
1) Affordable bike. Cheap to insure, repair, fuel, and buy.
2) Can be sold quickly. There area always new people entering the sport and every rider needs a first bike.
3) Small and nimble. Can be maneuvered easily under power and pushed around when not. Can park almost anywhere from sidewalks to unmarked parking lots.
4) Socially acceptable. Easy to convince loved ones it's safe.
5) Great to learn on. Everything you need to know about motorcycle riding can be learned on a 250cc. Any mistakes are generally not catastrophic.
Cons of a 250cc bike:
1) Generally a 1st bike. Prone to abuse, drops, crashes, neglect, and repairs/maintenance done by unskilled people new to the sport.
2) Limited interest. You will either exit the sport shortly after buying or move on to the next bigger bike. The next bike is generally a longer term purchase.
3) Less refined. There are more technologies on the more expensive bikes, although ABS and other traction controls are starting to make their way into the smaller affordable bikes.
4) Generally less stable. Larger bikes can handle the winds and road flaws better than lighter ones. You'll probably pee your pants the first time an 18 wheeler blows it's airstream into you.
