Hello,
That depends. Projectors need perfect environments/full light control where you put it, in order to not wash out the image. As for quality, a TV won't be able to show you as much detail as a 120" screen would, because UHD (not 4k) TV's that are commonly sold in stores are 65", with a few higher end larger sizes, but none that is affordable and 120".
Think of it like this, viewing distance is the key, however. If theoretically the 65" TV, and the Projector + Screen offer the same exact picture quality. Then say 10 feet viewing distance, you will see a lot more detail on the 120" screen, because a 65" isn't large enough to really make the super tiny details, visible at that distance. Think of it as looking at your arm infront of you, if you move closer, you'll slowly be able to see a lot more detail on your skin.
However, obviously it's not that easy to compare the two. High end projectors offer high dynamic range, once current UHD TV's get updated to HDR once the UHD blu-ray players come out, then unless you're in a basement, with perfect light control, you're probably better of with a TV. There's a lot to this, but hopefully you now understand.
All the best!