When I purchased my Tachihara there was only one model of Shen Hao available and no Chamonix. I picked the Tachi over the Shen because of the brighter Tachi fresnel over the ground glass of the Shen, the ability to use a 90 on a flat board with no need for bag bellows, and it was a little bit lighter. The advantages of the Shen Hao is that it's a bit sturdier and if you like using wide lenses it will take a bag bellows. As far as looks go the Tachi has been called beautiful and it's been called gaudy. It does draw a lot of attention. I actually prefer the look of the Shen.
I have never held a Chamonix but people who's opinion I trust on the Large Format Photography Forum say it's the sturdiest of the three. The Chamonix is kind of weird in that when you unfold it you have a loose front standard which you place into a hole and tighten down. Check You Tube for the video on this. From what I have read owners don't seem to mind this.
If you like metal the Toyo's are really nice. A very good friend of mine owns one.
Both the metal and wood Wista's have big followings but are a little pricier.