Trading is either "much more money", or "much less money", and anything in between, or even "lots of money lost". GPU mining is a lot safer since you can always just sell the hardware if the market goes down. When you buy coins and they go down, you end up with lots of useless "1-s" and "0-s" on your hard drive. And when an exchange goes down (where you stored your coins as most traders do — think mtgox and plenty of other smaller exchanges) then you end up with nothing. Anyway, this thread is about particular GPU (1080 Ti), so "mining vs trading" discussion is off-topic here.