You knew this post was coming, didn't you? LOL
They are both great speakers. I own two pair of the FBT Maxx 4a's and work them hard regularly, usually without a sub. They are very smooth sounding speakers with very strong bass output at 50Hz. There have been times when I've used one pair on stands and the second on the floor as subs, that is the beauty of having a built-in 3 band EQ with the low-band trim at 80Hz. They weigh in at about 33 pounds a piece which sure comes in handy when I have to haul them up a flight of stairs, like up at Grouse Mountain last weekend... FBT uses state-of-the-art B&C Italian made drivers with lightweight neodymium magnets on their lightweight speakers. Even their 10Sa sub has a neo magnet on the woofer and it is supposed to eat the Art 705AS for breakfast! B&C and RCF are two of the better speaker manufactures in the world, you can't go wrong with either brand.
I also own a pair of RCF Art 705AS subs that I can pair them up with on larger jobs but sometimes I feel that I don't really need them. The sound I get out of the four 4a's on their own is awesome and more than enough for most of my typical applications. I even did 50 kid school dances with that set up and the bass was strong and clear on the dance floor.
It would be a tough decision on which brand I would buy if I had to purchase again. A powered RCF 322A is priced much lower but has more output, but also weigh 50 pounds... The FBT 4a is believe puts out much more than they claim, cost a bit more but weighs much less.... According to spec's on paper, the RCF 310A is lighter and has more output then the FBT4a, it's also priced lower. I would like to do a head-to-head of the 310A vs. the 4a to see what would really happen. I just can't see a 10" powered box out doing a 12" powered box. But then again, that's exactly what the FBT 4a did to the JBL G2... Mike Pyle, can you shoot-out the two speakers in your store?