Each has a trade off, the GSX650 is a MUCH heavier bike than the SV650. Just from that I’d go with the SV650.
Also, if you are talking about the SV650S or 650N (faired sportbike look, or naked bike). The S has lower handlebars and might not be as easy on your arms as the N or the GSX650.
Have you considered the Gs500 or Ninja 500? Both are smaller and lighter than the SV ang GSX while still being plenty of quick. Depending on where you live, those 150cc can make a very large difference in your insurance. But in other places, they’ll make none-at-all (wish I lived in one of those places).