I personally find that fit is more about the top tube length; the amount the body stretches forward in the triangle it forms with the bike; rather than it is the amount your legs reach the pedals. This is determined by the crankarm length more so—and the Q factor.
Reminder that pros tend to use smaller frames, then supplement with a longer stem to adjust the reach.
You'd imagine this is to create a tighter, more compact package with the bike and the body, to maximize crunch output.
I'm 5'7" and recently acquired a 50cm frame to do just this. It's not built yet so I can't provide any more insight at the moment.
Both of those frames are geared to rather extreme road riding. Do you already ride a bike with similar geometry and it works for you? That Scott looks slammed, whereas the Cannondale looks like you could drop the bars a bit if you needed to.
For most people, a smaller frame + suitable adjustments to saddle and cockpit offers more options vs a bigger frame. I would always go for the correct reach and raise the saddle to suit your legs (but I'm no bike fit expert). Shorter tt + longer stem is invariably superior to long tt + too-short stem.
Hello Tomtom1988, why don't you try riding these bikes before deciding? That might help you. You can definitely adjust the seat, handle height, and handle angle to make the bike more comfortable. But again, try and see which one you like. And, please let us know what you end up going for..:-) Safe cycling.
I’m 5’10 with 32” inseam and I almost always go for a large because otherwise the bike just feels to small and crunched. I’ve rode smaller bikes where my knee will hit the bars when you’re turning or something but that’s just my preference. Also if you’re road biking it might be nicer to have more space as you don’t get on and off as much compared to a Mtb or something
One other thing to add, generally, when it comes to buy bikes is to ignore manufacturers' sizing labels (small, medium, large, etc).
There are no industry standards for these terms. They're probably worse than useless, as they tend to give people the wrong ideas about bike sizing/fit.
Geometry, particularly things like reach and stack, are far more important than alleged frame sizes. Of course, unless you've established the geo that suits you, through pro bike fit or accident/experience, it's difficult to know what geo works for you.