Well the fairly obvious one is, you said you mostly watch it for film watching, so 120hz 3d = 3d films, no 120hz = no 3d films.
That is entirely a personal choice, I got the Samsung 700D(the 750D is almost identical, different stand and the 700d has dvi instead of display port, both have hdmi), I rarely use 3d, it works fine, it works well and Avatar looks a bit better in 3d, still an utterly awful film though. I'm surprised by 3d, I bought almost exclusively for 120hz in games, smoother gaming and less tearing/stuttering feel in faster games partially as I suffer migraines and anything to reduce the eye strain can help. But 3d isn't half as bad as I thought it was, some people hate 3d, some people love 3d.
If you love it, then for films you'll have an entirely different option for those films that are done in 3d. 120hz also means for almost all screens, better response rate, less ghosting, less over drive issues which helps for really ANY moving picture which will include films for sure.
In terms of quality, the 700D over my older cheaper Benq led/60hz standard screens was mindblowing, its a stupidly higher quality panel and being a glossy screen rather than matt, its FAR clearer on text, reading, image quality, everything.
I can't see a reason to not go 120hz tbh.