For me, stand over height was THE arbiter, then sloping top tubes came in, more because of mountain bikes raising the bottom bracket height for extra clearance over obstacles.
Now, top tube length and thereby reach is my benchmark.
I've a Scott Voltage YZ Disc, medium, should fit me at 5'8"felt great in the shop.
......great for trialing, jumps etc but, for trails and roadwork it's awful....
Reason being the top tube is just too short for me, seat right back, still not right. The cockpit is too small and nothing will change that.
My Kleins and Marins fitted me like gloves, they all had slightly longer top tubes in their day.
Try before you buy
