An acrylic base won't fail after a dozen years like a tile base will.

If you do tile, I suggest doubling or tripling the liner. It will fail
at some point. (I don't know if doubling or tripling works, by the
way. I just think off the top of my head it's a good idea.)

Note you can get "pages" of tile. That is tile that is already
"grouted" together into "pages" that are perhaps 3 feet by 3 feet.
That might make things easier.

If you tile, be sure your backing board on the walls is concrete board
and not regular plaster board, as the moisture in the shower will
soften the latter over time.