I just bought a z650, those bikes are all very similar, also the sv650. I bought z650 only because it's the only one that's black, fz07/sv650 are both black/red

fz07: easier to power wheelie than z650

instrumental panel not as easy to see as z650 when you are wearing a helmet

stock front fork needs work if you plan to ride it hard on twisties unles you are super super light weight. (cheap fix if you do it yourself)

180 tires(IMH looks better than the 160 on z650/sv650)

z650: it will power wheelie in 1st gear if you try to, least powerful out of the three but they are all pretty similar. 1st year model, I hope there's nothing wrong with it. Front suspension is ok if you are around 150lbs, front fork is much firmer than fz07

sv650: exhaust sounds better than the other two, slightly more powerful on paper, classic looking, best suspension out of these three bike.

If you like to do wheelies in the future get fz07 or z650 and don't get sv650(long period of wheelie will damage sv650's engine since it's a v-twin). Otherwise pick whichever that looks best to you or has the best price.