I own both the GR07 and U700
If you don't need the lowest of bass and you take care of your iems, then go for the UE700 if you can find it for under $100. The GR07 is a little better, but it's definitely not 2x better. It has really nice bass, great mids, and the treble is awesome with the included foam tips.
If you sprung for the GR07, you definitely wouldn't regret it. I've been using mine for over a year, and it outdoes other IEMs that are worth twice its price.
Another option to consider is the Sony EX600. It performs at about the GR07's level.