Environment is better than "system", but I would still say "implementation".
Traditionally by "environment", one includes Emacs + SLIME + entire toolchain.

Descriptions are off.

I would qualify SBCL as "Highest speed. Great on Linux, Good on OSX, passable on Windows". The compiler itself is the slowest. It's the code it produces that's fast.

For CCL, I'd write "High speed code. Great on Linux, OSX, Windows. Commercial support."

For CLISP, I'd write "Most compact code. Most portable. A bit quaint. Not actively maintained." Base: bytecode.

For LW and Allegro, I'd write "High speed. Great on Linux, OSX, Windows. Proprietary platform."

Or I'd make a grid for how fast the code is, how well each OS is supported, whether it's free software, whether there's commercial support.