I have owned both. Had the Tachihara first but the copy I had was very well used and unfortunately was not as rigid as I wanted. Sold it and was looking for either a newer one or a Shen Hao and ended up with an almost new one of the later. It is heavier but depending on how much gear you want that difference might not make a difference. Neither are good for long lenses. At the wide end if you will never shoot wider than a 90 the Tachihara may be the better choice as the bellows are more usable at the wide end but if you want to go wider than the Shen has bag bellows which are very easy to change.
I think the main things to consider is the weight going to be important, do you want a selection of roll film holders (66,67,69 plus 6X12 and 6X17) and how wide are you going to go. In the end for me the deciding factor was which one I got a good deal on a slight used model. i am happy with the Shen and most likely would have been happy as well with a newer Tachihara. At first I thought I liked the more classic looks of the Tachihara but having had the Shen for a couple of years I actually like its appearance better. If buying new, either will give you decades of enjoyment and service. Good luck.