emaxx brushless motor decision

[Kajman]

Yeah. I want to limit power with ESC current limiter, I can set it to any number, it helps to keep engine and esc cool and when you don't need too much power, just cut it :)
But there is something like idle current, which I don't know what is, but more powerfull motors eat more energy even going slow than weaker, heard so, but not sure about it?
After reading several threads I think of 1521 1.5d, any idea where are they cheapest to get?
1515 2.5 DF why should be cooler?? By the same current limit set on esc?