Think of the Maxwell Titan X like having a Diablo, and the 1070 like having a Gallardo. Both are fast, both are sleek, one sucks more gas than the other and overheats like crazy, one is like a status symbol while the other is newer and just plain works. "Look at me, I have a TITAN. MWAHAHAHAHAHAHA."
If you could get either for $400, I'd be stuck between getting the 1070 or the maxwell titan too.