In article ,
says...

Yes well, I'm still not clear what the love affair with solids is all
about. Obviously, from the pure thrust point of view and their simplicity,
they have a lot to commend them, but when you consider you cannot throttle
them, stop them once started, and their tendency to vibrate due to the
chaotic burning and changing internal capacity, they would seem to be only
of use for lifting a lot of heavy fuel such as they tend to be used for in
Shuttle and other boosters.

Don't forget their failure modes. Large solids go "boom" (case rupture)
occasionally. Unfortunately when they do that, they give you little to
no warning, making crew escape "challenging" at best.

Liquids can also go "boom", but at least with liquids, you can install a
health monitoring system so you have a very good chance of shutting down
a bad engine long before it would go "boom". Design your liquid fueled
launch vehicle with engine out capability and shutting down an engine
doesn't even impact the mission.

Jeff
--
" Ares 1 is a prime example of the fact that NASA just can't get it
up anymore... and when they can, it doesn't stay up long. "
- tinker