That story of mine is old, but I have some newer anecdata: porting all my old project Euler solutions to SBCL and getting help by some better lispers than me to optimize it made SBCL come out close, but almost universally slower than Chez if someone really wants I can see if I find the code on any of my external HDDs.
It is hard to claim, because there are hardly any benchmarks. I just had the opportunity to move between the implementations and found chez to be faster for the kind of things I was doing, which was numerical stuff and loops.
SBCL is also an amazing project, and lately the GC story has gotten better IIRC.
Probably not, but the code is a hell of a lot cleaner! I looked through it and thought that even I could work on it. The new macro expander is even possible to follow :)
A number quoted is that SBCL preforms roughly on par with, but slightly slower than, java. For what it is worth, the computer benchmarks game confirms that: https://benchmarksgame-team.pages.debian.net/benchmarksgame/...
That was with optimize level 3, which burns on (car 1), and then you might as well use C, but the language at least allows for those speeds.