[BrianG]

Wow, going from "best bang for the buck" to "high end". :)

For 4s, either the 1512 2d (2600 kv) or 1512 2.5d (2000 kv, but out of stock right now)

For 5s, either the 1512 2.5d (2000 kv) or the 1512 2y (1400kv). The 2y might be a little too slow so you'd have to gear up a little.