The best suit is one that fits properly.
A lot of people down here use the thick ones from the Anchor factory outlet in Goodwood - they have a good sale on show weekend every year. I found they didn't fit me very well though. I got an O'Neil Evo 5/4 sent over from Pommyland - check the net for good sales over there at the start of their summer (start of winter here).
Smooth skin suits are generally considered warmer, as the water doesn't stick to it and then cool as the wind blows over it, but they will not last as long, especially if you stack a lot onto the board, or surf as well.
Don't listen to any advice from anyone from a latitude higher than Melbourne, they have no idea what this "coldness" thing is.