I've got a 2K setup right now with 1K of each over a 4x8 table...
There's a few very minor differences in the buds, but definitely nothing that's mind blowing.
The MH side:
Somewhat shorter internodal spacing
The HPS side
Slightly larger buds (but a hair fluffier)
Plants are a little taller
Since it's a quasi-perpetual SOG, I'm gonna run them the first 4 weeks under the MH side, then move them to the HPS to finish out...