I´ll personally always favorite orginal tile sets. Fire and Marble is some easiest to build IMO. Dirt & Rock is maybe toughest all orginal tile sets. Though both are good make some endurance levels. But making some sharph trick levels those boards are hard ones to build. At least Dirt.
Somereason i never are favorited special tile sets myself. Agony is maybe my favorite make special type levels.
Yes i myself used nearly always orginal tile sets when make level. Someone might find it just way too retro. Yes its my style make levels. I´ll always try add some special style levels my packs.