The deal there is that you'll get a potentially better dynamic (even crossing over to 80hz/small) using the 60's because of the extra bass driver, or more drivers! Why?...more emphesis on the affected frequencies, cancellation of distortion between 2 bass drivers, reinforcement of transients, more efficiency, etc.
The 20's, if I'm not mistaken, have 1 midbass (typical monitor), and the 60's have 2 midbass woof's, yes? All things equal, you'll have a bit better dynamic ability with more drivers. Again, all things equal. This advantage is certainaly more afforded, the bigger the room, etc. In a setting that's a smaller space, the 20's will sound more dynamic and powerful than in a larger space.
Also, the 20's "roll off" higher up (even though your processor rolls off bellow the "small setting") than the 60's, which will probably have more bass energy pressent bellow the "cut off" nonetheless. This is more noticeable in a small room, and less desireable often. In a big room, probably a benefit to reinforce what the sub's putting out bellow 80hz, etc.
Basically, in a larger room, the floor standers will sound sronger, while the 20's will be better suited (more than enough if set up right) to smaller spaces.
Yet, get either set up for proper coupling with the room, cross em over right, and you'll have good dynamics (If you don't treat acoustics right, you'll need to sit proximally closer with those designs, so you hear more "dirrect sound" vs. reflected...trust me.)
Good luck