I'll second the opinion that a "generic" table will be useful for several periods and rules than a "dedicated" table.
And in the long term that is a heavy factor to consider.
Moreover with CARNEVALE, because the water features and canals are a staple of the mood.
As for the rules, CiCarpathia is cheap enough (And a VERY GOOD set of rules, as I own them too) as to try and has a strog support from the manufacturers and a yahoo group, OTOH, CARNEVALE is free, and we can expect support, at least for a while, so no looses there.
In the end, it's all to you and how much time, effort and money you and your friends can and WANT to spend in your gaming table.
Hope that helps.