Hi David, Well there are tripods that are very solid and stable and then some that are not. The same holds true for portable piers. Usually a pier is a good design and can be the better of the two. But some makers of tripods have excellent designs.
It depends on the type of telescope and mount. If you have a Newtonian on a German equatorial mount, a tripod sometimes creates problems because the lower part of the tube tends to bump into the tripod legs. Otherwise, a good sturdy tripod with wide legs is a good choice and probably somewhat easier to transport than a pier.