I work exclusively in 1:72.
The reason being that a) it's what I usually built in when I was a kid, and b) my intention is to build as complete a collection of WWI aircraft as possible, so space will be an issue! This aim was first conceived when I was a teenager, so when I restarted modelling about 5 years ago, I picked up on that - not realising how many kits were now available - I have over 130 different types in my stash!
I do have a couple of kits in other scales: the Airfix 1:12 Bentley that I'm currently working on, an Airfix 1:24 Stuka, and a 1:35 Tamiya StuG III. All of those have been in my stash since I was a kid.
Apart from that, I enjoy this scale more than the others. It is not necessary to add every detail, and most detail that is required can be hinted at, rather than actually added. One thing I've noticed with the Bentley build is that I have to add every nut and bolt - this requires much more accurate references, most of which are extremely difficult, if not impossible, to obtain....
Ian