In terms of performance the Optimus 3D and San Diego are probably (though never having owned an Optimus 3D and never having seen benchmarks for it either I can only guess based on the spec of the processors) roughly comparable in terms of performance. Essentially the choice comes down to what network you want to use it on (if Orange or T-Mo, go for the San Diego, if anything else then the Optimus 3D) screen size vs screen resolution and probably the most crucial factor being whether you can live with the San Diego's lack of expandable storage.
Oh great now I'm getting seriously confused on what to get. Not too long ago the G300 came out and now this. My OSF is refusing to charge and I need a replacement! This phone looks ridiculously sexy with all that glossy front and hard-ish plastic back... and curved edges.
Ahhh.. curved edges.
What do you reckon, I go for this or buy the LG Optimus 3D which came out last year? Would it perform better than that? To be fair last year everyone was saying "Faster than ever" ... and now they're pretty slow
The G300 is far less capable than the San Diego (which isn't to say it's a bad phone, it's just not got the same power behind it) but it is essentially the new ZTE Blade, so it has the community behind it, so as Tilal says, if you want to mod go for the G300.