So yesterday I took the 20 off the back of one of the Roads and placed it on the 700 (sacrilege I know, but bear with me).  I only rode it up and around the corner just to see what I felt like.  It reminded me of being down on the ole Speed!  Laying way back and feeling comfortable.  Anyway, got it going and noticed right off that I was topped out in gears.  I turned around and could take off in the highest gear in the back (11 I believe).  I most likely could not do this with the 700 wheel.  
 
Now I understand all the technical 'facts' about the big wheel vs. small wheel, but what does it FEEL like TO ME?  Well now I know.  With that 20 in the back, I could easily spin out and would have had to use the big gear up front, if I was out on a longer ride.  I also know it changes the geometry of the whole trike and Catrike says not to do all that...yada, yada.  But I had to know and now I do.  Funny thing was I kinda liked the feel of it...but I was only on a very flat road for a short time.  I suspect some of the hills that slow me down when climbing, would not be so tiring to climb- but would also not be as fast coming back down...so for me the difference in the FEEL of the trike with a small wheel, might be something I do when I'm out on a family ride...then I wouldn't always be holding back.  It really didn't seem to affect handling much at all.  
 
It also let me know that if I continue to work out with the 700 wheel, I'll be stronger and faster in the long run.