The difference are from where you place it and what you place it on, tiles, carpet, behind the lounge etc.

subs are designed to be hidden under chairs and generally out of sigth and since the sub fequence is a large wave form you don't need to position it anywhere within the stereo space strategically.

For me down or up is just a marketing thing. If you have to ask which is better then you aren't listening to either of them. Try befoe you buy.