I play a lot on bar boxes, and occasionally on 9ft tables when I can.
I'd say for the amateur, a 9ft table is daunting and kills their confidence in their shot making, so it winds up being a much harder table for them. The crowding of a 7ft foot table isn't a problem for them yet, their skills aren't there for it to matter.
I noticed for myself the 9ft tables became easier to manage when I got confident in my shot making. Turns out, if you can pocket a ball from 6.5ft away, you can also make that same ball 8.5ft away, nothing changes except the perception in your mind. Once the anxiety of the table being a little longer was gone, it felt like I had room to breathe and open my stroke. I find myself running out more because I am getting better leaves even if my positions aren't spot on. Coming across a shot line on a 9ft table gives you a lot more room for error than a 7ft table. I also noticed I can really get a consistent good spread on the break which leads to more break and runs. On a 7ft table, unless I find the perfect break speed, the balls always find some groups or die on a rail because of how many times the balls hit eachother and the rails. It's like a bad pinball machine. I've experimented with soft breaks on diamond 7ft tables, and I've never been able to consistently pocket a ball and get a good spread. It feels like I am either getting a good spread with no balls dropped, and my opponent runs out, or I smash it and pocket a few but have some problems. I don't have half as many of those breaks on 9ft tables where I can let it out and not have problems.
Now days, I just get my ass kicked on 7ft and 9ft tables, but mainly play 7ft tables cause there's very few 9fters around, and all my leagues play 7ft.
If I ever have a home with enough room, getting a 9ft no doubt.