I would murder babies to get FiOS. I clearly cannot recommend it, however, having never tried it before, but 100Mbps to my door sounds so Goddamn sexy.
I can tell you that cable Internet (which is what I assume Cox is offering you) is unreliable. We have Comcast here in Georgia and that shit goes in and out like satellite TV. I use AT&T personally, and while their nightly peak traffic shaping sucks balls, the service NEVER goes down, which I almost require since I work remotely quite often.
If you get FiOS, please let us know how it is!