neither I guess.
I use an into the corner arrangement, have tried both of the others. My short dimension is five meters, the long around eight. So either way it should be pretty good. If IO go short, then I have an equivalent wide FR situation, if I go long then space behind me and the speakers. There is one confounder, a bay on the short dimension which I think 'focuses' the rear reflections straight back to me at the lp.
Anyways, I stumbled upon a writeup on the decware site where he was kinda 45 degrees into the corner. Supposedly reflects those FR away from you yada yada.
That way I have found is vastly superior to either of the other methods. Guess it is not too waf friendly but as I have my own room where the missus does not care what I do it matters not.
A bit of fiddling with placement as always, so I did not end up exactly 45 (had to balance the virtual volume either side, which takes into account the bay on the left) but this has given an immense soundstage with depth etc.
Interestingly, I went back to the 'optimum/usual placement as an experiment, revisit it to see what happened. Lost all the depth, lasted about a day and back to this setup.
I spose many do not have the luxury to do what is best, so automatically go to the accepted placements, which leads me to wonder if many do not have the best arrangement of the system (or alternatively do not have the physical space to be able to try). It prob would not occur to many to try these oddball setups, which are free tweaks that in my case at least gave marvellous results. It was a royal PITA to do these wholesale rearrangements with an active four way plus subs! But boy I am glad I tried them all.
I wonder sometimes (given the above factors) how many unrealised improvements are out there when people are looking to spend money (new gear etc) to get improvements??