I guess that depends upon your definition of each, but from my understanding of what you mean, I would have to say
"realistic". The reason being that the AI is pretty temperamental at the best of times, and bizarre terrain can severely unbalance a game's playability and the challenge posed by the AI.
With that said, if well considered, unusual terrain characteristics can lend enormously to the individuality and intrigue of a scenario (or game on pre-made map). Care, thoughtfulness, and playtesting will point to whether a 'surreal' set up is workable or not.
[Because I still can't spell
....]
[This message has been edited by Cam (edited May 09, 2000).]