I generally go warm way, but that is because three of my hives are that way. No choice with many hives, eg Langstroth. They have no issue with it and do not debate it! It is that important!
I would disagree with MM in that a small colony would always be warm way as the nest will be nearer the front wall and wasps may be easier to defend against with that arrangement (IMO).
Do you want to work from the back of the hive or the sides? More choice if cold way!
Solid floors or OMFs? As MM says, not a lot of difference with an OMF.
Time of year? I suspect it has been quoted many times that the National is better than the Langstroth, because warm way is needed more in Britain than America, and there is a choice with a National. Doesnt hold up to scrutiny though. Narrow, shallow entrance with a solid floor is not much different either way. So I suspect it is only during the cold British summers that warm way might be chosen for the temperature aspect.
Take your choice. Even my fixed warm-way hives (the Dartingtons and beehaus) are generally worked from the side anyway, so to be honest I don't personally care a jot - except that I find that with the 14 x 12 frames the foundation seems be completed better (and more evenly) if warm way - almost forgot that.
Regards, RAB