Which do collectors want more, sets or lots?

I'm selling off some old toys, including a number of Bionicle sets. There have been a few that are built and complete, but most of them are only partially built and otherwise in pieces. There are definitely enough pieces that I could probably gather together some complete sets; and while this would be my preference, it'd also be very time-consuming, and for the effort I'd want to try and make sure that I'm offering something folks are looking for.

So when collectors are buying, would they want complete sets? Or should I just sell the whole thing as a "mixed lot" and call it a day?