Hi Adam - this was an experiment which was eventually aborted (memo to self - really must find some time to update that website).
With the exception of some drone hives I have farmed-out a quarter of a mile away, I operate a single-yard apiary within a nectar-impoverished area I call 'cabbage-country'. So robbing during the season is pretty-much guaranteed, and all of my hives have some form of anti-robbing device in place - mostly in the form of screens.
With that multi-hole experiment I'd completely forgotten about the robbing issue - and when it broke out (in early August if memory serves) I then had to coble something together pretty quickly in order to save the colony. Such a large screen pretty obviously then affected their choice of entrance hole - but prior to fitting the screen it appeared that their choice of hole (both for entering and exiting) was fairly random. If indeed there
was any preference, then this wasn't at all obvious.
FWIW - for the last few years I've been running several hives with both top and bottom entrances (American influence from my time posting over at BeeSource) and the bees seem happy enough with that configuration. I was initially very leery about doing this as I've always been a 'sealed-top, OMF with a bottom-entrance' type of person, but so far there have been no problems.
But - I'm about to start making a dozen or so custom 'deep' bases (incorporating Slatted Racks and so forth) and these will have bottom entrances - which shows that I'm not completely sold on the American way of running hives ... at least, not yet.

'best]
LJ