I've been working with eZ80 on Agon Light and the performance ceiling is considerably different. Both the clocks and the instruction timings are more generous owing to a three-stage pipeline, so while interpretation is still slow, and it's got a clear preference for either 8 or 24-bit(in ADL mode), it is now a Z80 that can be applied productively to high-level code operating over 32-bit values...

...except that the BBC BASIC was giving me Heisenbugs, so I had to give up on it. So I'm on Forth now, and immediately found that Forth is a more productive environment than an early BASIC anyway. Linenums add a killer amount of bookkeeping.