Honestly neither, but if I had to pick one, it would be Zoom. Zoom is essentially just a cash game, where you play against new opponents in every hand, so you are still put in complex postflop situations, where skill edges will show. The main difference to normal cash games is, you have less reads on the opponents, and things like history and dynamics dont exist. You will never know for instance, that someone might be on tilts, because he got sucked out on in a big pot the hand before.
Spin n Gos on the other hand are shorthanded hyper turbo SnGs, where 3 players (the PokerStars format) start with 25 BB and compete for a winner take all randomized price. They last an average of 8 minutes, so they are great for people, who play on their phone and have time for one in their lunch break or in the bus on their way home from work.
Some people say Spin n Gos are beatable in spite of a high rake, but I just dont enjoy playing them. I had a session, where I played like 8 in a row, and I felt almost like, I was pulling the handle of a slot machine. “Would you like to play another – yes”, “Would you like to play another – yes”. Nothing bad to say about people, who enjoy playing these, but its just not for me.