I find it has a lot to do with the room their in. Some rooms suit JBLs a lot better than others... there's a bar in Kingston (called Brandee's) where JBLs just seem to suck no matter what... they have a nice spike somewhere in the 2-4 KHz range that just makes the room ring.

The main thing I like about the JBLs is their weight... if you're a travelling band, weight has a tremendous affect on gas consumption etc and can make a big difference if you're out on a long haul.