I've used both techniques and now find 'constant aspect' the more consistent. However! It might be a big however the main reason for this is that I fly from farm strips and over the years I have tended to stop flying the airport, transport command circuit and instead fly a circuit where I could genuinely glide back to the field I have left!!(was that the underlying reason for a 'circuit'?). Anyhow this sort of practice - which would make you very unpopular at most GA fields is virtually a 'constant aspect' approach. So my PFLs are very close to the majority of my farm strip landings. And as practice makes perfect, or at least better, so my PFLs tend to be pretty reliable.
So if all the approaches you have every flown are from conventional circuits by all means try the constant aspect - but remember that all your visual clues for action are no longer appropriate. This is suspect is why the high key low key method is generally taught to PPLs - it draws from their existing experience.
Given enough practice I think constant aspect is the way forward - but it does need significant practice. Given that I get nose bleeds if I'm more than 2000 agl it means I am always close to the low key position, so half of the technique is no good to me. Constant aspect actually helps me choose the arrival location because in a short wing Piper the glide is between 7 and 9 to 1 - so if it isn't close forget it!
Cheers