Do 801's actually run cooler than 901's or is it just the length of the atomizer chamber that allows it to cool? Moot really as the vapour is cool when it reaches you. The be112's are very nice, as far as 801 class atties go, not tried the sub version of an 801, I would imagine it is very similar to a 901 (don't know who makes the stub version, doesn't really appeal to me, heard about it through some supplier spam).
The 510 basically runs hotter, as everyone has said, but given that this is the day and age of custom resistance atomizers you can get 901's that run at 2.2 ohm, ala standard 510. Despite also having LR 901's and 510's myself, I haven't really taken any notice if they have different characteristics even though they have the same low resistance (~1.7ohm), all I know is they pump out the vapour and actually perform like I expected original e-cigs to do. The future, today.