The shadow is faster than a 250.
It only has 38hp ( http://www.bikez.com/motorcycles/honda_vt_600_c_shadow_vlx_2002.php ) but it has 35 foot pounds of torque. Because of the very tall gearing (only four gears) it accelerates in a very “lazy” fashion, but it is still fast enough to out accelerate traffic. I am speaking from personal experience here.
If you’re ever in a situation where you are in physical danger because the bike isn’t accelerating fast enough then:
a) use your brakes
If neither of those are options, then I’m sorry but you’ve screwed up pretty bad and made a long line of mistakes to get there. No matter how fast the bike, in a reaction situation it will accelerate slower than it can decelerate or swerve.
Aka, don’t try to get in front of the guy who’s about to merge onto you, hit the brakes and drop back a car length, it is faster – or better yet get into another lane. If you are boxed in on three sides and the only option is to accelerate you’ve made several serious errors already.
Vulcan 500 makes 33 foot pounds of torque ( http://www.bikez.com/motorcycles/kawasaki_en_500_vulcan_2000.php ) which is less, but the engine can spin higher to produce more hp, and more importantly, it has a 6 speed transmission to let you stay in the powerband better.
The S40 makes 33 foot pounds of torque, put htrough a 5 speed transmission ( http://www.bikez.com/motorcycles/suzuki_ls_650_p_savage_2003.php ).
I own a 2003 Kawi ZZR-250 (basically a Ninja 250 with a slightly more powerful engine, 36hp at crank, and much improved suspension). My previous bike was a Honda Interceptor VF500F.
My parents own (and thus I get to play on regularly) a 1983 Suzuki 450GS and a 2002 Honda Shadow VLX. Mom had a 1983 Honda CB250 Custom (old Rebel).
“The two seconds between ‘Oh S**!’ and the crash isn’t a lot of practice time.”