Shells are lighter, dry faster, tear easier, have no inherent buoyancy
and require undergarments for warmth. Neoprene suits are more rugged,
have some inherent insulating properties, but are bulkier, much slower
to dry (as in 12+ hours) and have some inherent buoyancy.

This question was recently posted to a local dive club list, and one
response that stood out was from a member with four drysuits (all DUI).
He had two that were crushed neoprene and two TLS350s (shell suits). He
never used the crushed neoprene suits after he got the TLS'.

Getting a shell suit custom fitted goes a loooong way towards making
them comfortable. As this guy said (Perry Armor, for those who want me
to put a name to the story), "putting on a stock TKS is like putting on
a hefty bag."

Alan