I find that the numbers (400, 450, etc.) are more marketing than real world....

you need to look at the Kv, amps, watts. etc that a motor can handle
at 890kv, that is prety low for the 450...

so to say that the 450 is more powerful than the 400 (while logical) is comparing apples and oranges.......
the numbers mean little....

for a 15oz plane....something like the Hacker A20 would be excellent.....