The Zen has a broader(read taller) fusalage, and by looks seems to have more area, and the canopy is further forward on Zen, TaiJai has a sleeker look, especially in cowling/canopy area. Zen does seem to knife edge better then TaiJai. Also the wings are slighly different in configuration. Both are still double tapered though.

The Zen has counter-balance on both elevators and rudder. TaiJai does not. The belly pan attatches slightly different on the Zen, it has alignment wires and the whole pan removes from the rear wing-mount to the firewall. TaiJai only removes the width of wing-chord, this could make difficult removing if you run a tuned pipe.

At one time not to long ago, I had both Zen and TaiJai. I sold the TaiJai. TaiJai had a .46 w/pipe(2-stroke), flew really good and solid. I would say if describing it using a car as example, it might be Z-28 performance. Fast, good handling, kind of pipey though due to engine pipe combo, and it was loud with a definate power band. Very good vertical but would fall off if not hit just right, and it was high although limited.

My Zen I still have, and it's one of my favorites. OS70 4-stroke, stock exhaust. This plane/engine combo has absolutely unlimited vertical. It's not as fast as the 2stroke was, but it has so much more torque it's pathetic. Idle along, point nose up gas and go. Like I said it's not real fast, but handling wise would be a tricked out Corvette with bells and whistles. Yet it's very smooth when you ask it. Turns on dimes though.

This is only my experience with these planes. The Zen seems to fit my style of flying. Maybe it's the engine combo too. Don't know that one. I've also known guys that really like TaiJai too. I thought I did until I met Zen.

Also small trivia on Zen, it was designed by Christophe Paysant Le-Roux. One of the TOC 's finest. He also designed the "Madness" 3-D plane. If you look at Zen and look at Madness side by side(I did) they look strikingly similar in overall lines although Madness is total 3-D and a very enhanced version, and the craftmanship really shows. Madness is a REALLY nice ARF if you can get them. We're talking sport pattern here though, sorry didn't mean to get lost there.
Mav, look around and see if anyone has them around your area, and look each one over carefully.
If you want a good look at a Zen, come on over to Fresno. I've got the Zen50, and there's also a very nice guy that has the TaiJai60 w/YS91(real nice plane).
Good luck to you , I hope this helps.