Definitely OTK - the more old-fashioned the spanking is, for me, the more fun it is.
Subjecting somebody to time-honored old-fashioned discipline punishment is - somehow - MORE embarrassing and mortifying. And that's the fun & the turn-on.
I don't like the bed being involved in any way, if possible (sometimes it's the only option, then I shrug & will go along). Why? Because I do not like mixing in sex with spanking discipline - and a bed infers exactly that (to me).
A sturdy chair in the center of a room is best for administering the old-fashioned spanking. Right? Tried & true :-) And whether the person being spanked is male or a female, either experiences some humiliation going over the knee with their bottom bared for slaps/punishment. If a bed is involved, minds wander to OTHER outcomes (I think), and the intense focus of what a spanking should be gets muddled.
Now a whipping - such as with a strap - is not necessarily best delivered while on a chair dealing with the OTK position. But my personal favs, using hand or back of a hairbrush, benefit greatly by making use of OTK. (Whippings - I'm not thinking of floggings etc - can be great fun administering when the "victim" is bound up with his/her arms stretched way high over their head, & sometimes when forced up helpless on their tip-toes).
Another issue: victim clothed or not clothed? Because I can enjoy either - honestly. Spanking the seat of the trousers can be great fun. The ideal is - predictably - a bare bottom. But.