Well, if you have all the albums, then Mothership is a bit useless to have, since there ain't nothing new on it. If you are planning to buy all the Zep albums in the future, then purchase them one by one and leave Mothership for what it is.....all albums are worh having them on vinyl, and the artwork is just better in LP format (well, at least that is my regarded opinion).
The cool thing with TSRTS is that it differs from the original album quite a lot, so both the TSRTS albums are worth having, the old double LP and the new 4LP version are both cool.
If you want to have just a great collection to start, then go for Mothership, or try to get a copy of Remasters on LP (six disks with the best songs and some rarities on em).
As soon as I can make pics again I will put some pics of the vinyl TSRTS on here.
Hope this writewrite was somehow helpful......greetings.....Res.