The only other compiler for 6502 I've ever used (and had to modify) is the old cc65. The original author stop developing it (10+ years ago):
https://cc65.github.io/
I experimented with cc65 and wrote a simple game that ran on my actual C64 hardware. It was a lot of direct memory access, unrolling loops, and avoiding stack usage. A fun time overall, and it ultimately ran smoothly, but I see do why people who attempt anything serious on a C64 tend to focus on using ASM.
The only other compiler for 6502 I've ever used (and had to modify) is the old cc65. The original author stop developing it (10+ years ago): https://cc65.github.io/
But there is some development ongoing: https://cc65.github.io/
Would be interesting to see comparison with the new one.