Sizing Question (how big of a difference do you think?)

So my Premium 3 ring frame has a 20.75TT and a 13.5"-13.75"CS Length, if I were to get a new frame such as the United Dinero, which has a really short rear, would my bike feel the same as my current frame size?

So in other words, would my 20.75 premium with that chainstay length, feel somewhat closer to the same with a longer top tube sized United Dinero?

My Frame:
20.75 Top Tube
13.5"-13.75" Rear End

United Dinero:
21" Top Tube
12.9"-13.5" Rear End

yes I know only a quarter top tube difference but this frame also has a steeper head tube angle.

a major point to why im asking this is because i have long legs, im only 5' 7" but on a 20.75 my knees can almost touch the crossbar of my handlebars so i figured i could get a shorter rear end and longer top tube to balance out size to geo feel