I think the non-tower maps end alot more quickly, but takes more thinking to succeed, due to the fact that any enemy can jus waltz right in and create Havoc b4 u even know it otherwise.And, BTW ive seen Nod get their arse's kicked in non-tower maps really quickly a moderate number of times, usually from a complete lack of teamwork.
And i think the n00b infestation we all got at the beginning is slowing down now, as ive been seeing alot more people actually interacting with eachother and typing stuff(me included). Plus GDI and Nod seem to be winning = #'s of games overall nowadays