I find water maps to be the quickest path to victory. Obviously some civs have bonuses on these maps (Lizzy, Kamehameha, etc.) and I won't disagree that a select few are designed for single landmass/few landmasses (IMO just Shaka and Genghis, maybe Harun.) But the majority of the civs aren't weighted either way and I find they perform better on water maps (Monty, Neb, etc.)
Reasons:
1.) You're almost guaranteed to avoid a carpet of units approaching your empire before turn 75. The only one who can do it is Kamehameha and he won't.
2.) Kind of an exploit, but the AI's inability to wage naval war is easy to capitalize on.
3.) Dom victories require sniping AI capitals, which is much easier on water maps. On land, you have to bulldoze through their empire to get to the capital but on water maps you can skip right to the victory condition.
4.) For all other victories, you usually just want to be left alone, and that happens MUCH more frequently on water maps.
My LEAST favorite maps seem to be everyone else's favorite: continents. IMO, it's the worst of both worlds: land maps give you lots of trading partners and let you meet everyone quickly and establish WC upon discovering PP whereas water maps have the aforementioned benefits. On continents, however, you can't meet everyone until after astronomy, you still have the worry of early rushes, have limited trading partners, and have to bulldoze to get to capitals.