A lot of it is personal preference, but you would
have to have used each one to decide.
IMHO, the most solid and (relatively) bug-free, is
SuSE Linux. It's install defaults seem to be as
good as, or better than, most other distributions-
especially for new users.
Redhat is probably the most popular (more due to
marketing than anything else), but has its share
of problems.
Debian is good, although odd at times.
Mandrake is also good, but they nailed their
configuration files long ago, and are sometimes
hard to decipher.
Most all of them attempt to keep up with the
latest drivers, and it seems that there is a
trend to adding tools to use others install and
configuration files.
<als>