The SV is a V-twin and the 650 is a parallel twin, and both are tuned to generate their power in the lower rev ranges. This makes them both pretty street and beginner friendly, and certainly more so than most parallel 4s.
This is not to say that parallel 4s can’t be detuned to make their power lower (many sport tourers do just that). But all things being equal (and they NEVER are), V-twins, followed by parallel twins are more often built and tuned in a manner that makes them more beginner friendly. Meanwhile, many parallel 4s are built and tuned to take advantage of their inherent abilities to rev very high and put out high hps.
There are a lot things that go into comparing various bike and engine displacement is often one of the most inconsistent measures. That’s why sometimes, 650ccs feels smaller than 500.
+1 on the idea of sitting on lots of bikes. Printed specs and recommendations can only take you so far. Eventually, how the bike feels under you will make all the difference in whether you love your new bike.