if you would have to choose if to buy 3 Gtx 1070 Ti OR 2 x Antminer L2s which one would you choose?
Don't use a deciding factor the resale value please.
Antminer L2 is scrypt based ASIC, means, only scrypt based coins you can mine. May you need to take a look around about scrypt based coin beside LTC. If you found a lot of coins that you can mine with good profitability, go for it.
GTX 1070Ti more flexible in the algorithm. Can mine several algorithms and powerful almost in every coin.
I'll go for GTX 1070Ti.