I am 6ft and went for an 18.5 in frame, only thing was the height of the bars. Solution was a stem raiser, cost me 320 at
Evans, took me about 15 mins to fit (took my time to get bars straight) I now have a very comfortable upright riding position , done 15 miles on 1st part of my ride yesterday without stopping. Overalkl 50 pain free miles yesterday and same on saturday. Also fitted Ergon GP1 grips and adjusted brake levers and gear shifts down to avoid strain on wrists, now have a very comfortable bike.
The other bike is a hibrid 21in frame which I was told when I got it was the right size for me, but have always found the reach from the saddle to the bars a bit of a strain, hence why the smaller frame this time.
Stem riser was very easy to fit.