Go with a projector and screen. I would personally wait for 4k until it's more mainstream. You can get 4k blu rays for the same price as a 1080 blu ray, but that 4k blu ray also includes the 1080 blu ray discs, so you can easily start building a 4k collection now, without having to worry about purchasing the same movie again in the future.
A 75" TV may seem big, but it really isn't judging by your room size. And, the DLP projectors don't have a problem known as "screen door effect". They also have the fastest response time in any display type right now, down to about 15 microseconds. This means that there will be absolutely no ghosting, ever. This makes for a perfect 3D watching experience, TV's aren't even close in terms of "sharpness" if you will, in that area.
I'm a movie enthusiast, and I just went out and bought the Optoma HD141X. It's a $549.99 projector, 1080p 3D. The important part is the screen. Buying a $2000 projector is bad if the screen is not very good. If you have full control of the light, or nearly full control, as in no light sources are directly going to bounce on the image, then go with a projector.
I'm 8 feet away from a 78" projector screen, and when watching movies it's too small, it was too big for approx. 2 days. That's because blu rays crop 30% of the image due to the black bars.
With all of that said, I highly recommend buying a TV which has got HDR, if you're going for 4k, as that's the main reason to upgrade, no because of the resolution. At the end of the day, you should try both at a store or something if possible, because you won't know what you want until you try it.
However, nothing can simulate being at the movie theater better than watching on a projector and screen, not just because of the size.
For the record, a very popular projector called W1070, is going to give you about 150" screen at 15~ feet, ~12 feet if you use the optical zoom. That's 4x more screen area than a 75", that's a 10,8 feet wide image.
All the best!