The SV650 is a V-twin (2 cylinders in a 90 degree V orientation). The CBR600 is an inline 4 (4 cylinders in a line). The SV delivers its power (torque) fairly uniformly over its rev range which allows the rider to be less concerned about engine speed/what gear you're in. The SV is also quite light and handles very well especially with the right tires and suspension set-up. Most inline 4's deliver their peak power closer to the top end of the engine rev range (near redline). Consequently, riders usually have to pay more attention to keeping the revs up (being in the right gear).
An SV actually develops about 68 hp stock while a CBR600 F4i develops closer to 100 hp I believe. The F3 and F2 weren't quite as hot (but still enough to get someone in trouble).
For a lot more info on first bikes, do a search on "first bike" on this forum.