As Tichu is considered the pinnacle of climbing games then the relevant comparisons amongst trick-taking games would perhaps be more in the line of Tarot, Skat, Doppelkopf, Mü etc. Even though Spades is a good game, there are quite a few more interesting ones out there. The same guys that play Tichu probably would be happy to play a lot of trick-taking games (unless they view the partnership part as a key), but you should try selling them something else than one of the simplest ones.
Spades simply has nothing in common with Tichu (besides the fact that both are card games) so I don't see the relevance of the comparison at all. There are *very* few good partnership games so Tichu can kind of dominate that market. makes the playing experience more social otherwise the competitors are indeed almost as good. In comparison to those the answer would be easy the key difference is the partnership which e.g. After your first post I thought you referred to games like Gang of Four or Haggis that are mechanically similar to Tichu.
