Hi,

Welcome to pattern…

I have a Zen 90 powered by a YS110s and it flies super, in some respects even better than my 2 meter ship (which is an old design powered by an RX140FI).
The Zen 120 flies the same as the Zen 90 (there is one in my flying field).
I have flown a friend’s Swallow 90 powered by a Saito 125 and my Zen 90 is so much better.
So as far as the airframe goes the Zen 120 is wonderful plane, far superior to the Swallow IMHO.
However, you need to put the right power plant in the nose which means a YS140 sport or even as suggested above an RX140 (that one must be a real blast!!!)
As for the Leo110, I have never seen one fly and it looks real nice however the downside is that this one is a little bit heavy as some CMPRO planes tend to be.
It was designed for the YS110 (hence the name) and at 4200-4400 grams (this is what CMPRO themselves wrote on the box if I remember correctly), I would not dare to mount a lesser engine on it.
So if you are “restricted” to one of these planes then the best choice is a Zen 120 however the correct one for your current engine would be the Swallow 90.
Mind you, even with the Swallow 90 you are not going to have a lot of vertical ability with your FX91 and a standard muffler (it is a CMPRO kit, remember?), so when you get to perform the more advanced schedules you might want to ditch that muffler and install a tuned pipe.

Good luck,

Danny