I mostly used jetty while rapid prototyping with Solr. Because Jetty is packaged with Solr, it was very convenient to use. However, we use Tomcat6 in production. It was easy to transition.
I would say go with what your most comfortable with initially.
According to the Solr Wiki:
"For non-trivial installations, JettyPlus is recommended."
http://wiki.apache.org/solr/SolrJetty