sub+satellite or full range?

"Subwoofers are in almost all houses now." I bet to differ. I would be that if you polled American households less than 15% have subwoofers.

WAF, cost, system size.

If you're talking for music, I'd be a bit more cautious than many of the above replies.
Traditional subs were designed primarily for the low frequency effects of movies, not music. Given that such LF noises are not directional, you just had one sub.

In sub/sat systems for music, the sub has to do a LOT more work, and is responsible for much of the mid bass (and even low midrange) frequencies, depending on your choice of satellites (and therefore crossover freq). These frequencies ARE directional, and you may find your stereo imaging suffers.
If you use very small sats, I'd seriously consider using two smaller subs to preserve the stereo information of the lower frequencies, or otherwise look at small fullrange wall-mountable speakers (eg B&W 686) + single sub.

IMHO I prefer the sub sat. Something like a Proac Response 1SC and a Rel sub. I had the original response 1s and loved them with my Velodyne servo 1200 subs. I sold them and experimented with a few high end speakers ie. built some North Creek Rhythm speakers, then had Merlin VSM M and now Tyler Linbrook Signature one piece. I just purchased and built a Proac response 1sc clone. The Tylers are soon to be for sale. Imaging on these small speakers is amazing. Listen to the Proac Response 1sc and you will know what I mean. Other small speakers will probably image just as good, but I am not familiar with others like I am with the Proac.

great responses, thanks to all.