A GigE switch is cheap, and a GigE port is easy to add, or you can use the existing one on a system. AoE sits down below the IP stack so there is little overhead for comm, and it looks like a SATA drive in most ways. The primary vendor's appliance (www.coraid.com) will take a rack full of SATA and make it look like one drive via various RAID configs.
Yeah FC is faster, but how many drives are going to be talking at once? Are you really going to fill the GigE and need a FC to alleviate the bottleneck? If you are then FC is probably not the right solution for you anyway.
Your mileage may vary, but I expect anyone will get comparable results for the price, and many will get excellent results overall.