For a game that edges towards the lighter side of moderate complexity, I prefer a single page sheet. If the spells, tech, gear, etc. is really involved, then I can see a second sheet for that. But I want the things referenced most often in play on one page.
I also like sheets that aren't "fussy" with ornate boxes for numbers and decorative flourishes. I'd rather have info than white space, but if the game is light enough (e.g. Toon) then by all means make use of the white space. This is where my first preference dominates: I'd rather have a slightly crowded, plain single page than going to a second page and then trying to find stuff to fill it.
Of course, the more info on the sheet, the more arrangement matters. It needs to guide the eye to logical areas.
It might not be surprising that it is very rare that I like the official sheet of a game as much as some fan-produced alternative.