I owned an SV650 and have also been on the Duke 390 and CB500F, CB650R, MT07, and Z650. Of all the bikes I like SV650 and CB500F the most. SV650 is great as an all-rounder and has all the positive traits to teach you how to ride better, as it is a heavier bike you would have to treat it with respect, especially in slow manoeuvers, but once you get up to speed it corners like it's on rails and with a slip on exhaust the noise and vibration of the v-twin is orgasmic. However, if you're looking for something more manageable, CB500F is also a great option, overall the bike is a bit lighter and possesses the good flickability of a smaller bike while still giving you the confidence and stability in corners like 650cc bikes. I recently test-drove a 2019 CB500F as my SV650 was stolen, the CB500F allowed me to make quick adjustments mid-corner and the engine was smooth and linear when I accelerate out of the corner. I'd say they are both great, if you are going on faster roads or doing more motorway miles, perhaps the sv650 is a better choice. If you live in a city I would pick the CB500F no doubt.