In 2006 I wrote a complex multi-threaded socket and web server that talked to MySQL. I wrote it first in ACL, ported it to CMCL, then to Ruby, and then parts of it (with another programmer) to C (ultra high performance after that). So I got a head to head comparison for the same task.
As to libraries in 2006 (and Ruby libs are only better now). It was easy in Ruby to find libs to talk to third party APIs like Twitter, Facebook, Photobucket, etc. None of this existed in CL. They might be quirky, but they were there.
In ACL/CMCL "core" libraries like sockets and database access tended to be missing a lot of "fringe" (not really that fringe) features like transactions, multiple database support, enums, bigints, etc. But worse than that they tended to mysteriously hang under moderate volume. I found this true on both ACL and CMCL, different libs.
The equivalent Ruby libs, like ActiveRecord, had some SERIOUS quirks, and were missing some of those "fringe" features (I added a lot of them like multi-db, enums, and bigints). But fundamentally, they were more modern in design and reliable. ActiveRecord almost never crashed or hung. Yeah, it did some crazy and stupid things, and performance was a problem. But it didn't hang. When writing real production code mysterious hang/crash/corruption bugs are just a deal killer.