I've lived in both attached and detached. Of course detached are better in general, but if you're buying newly-built homes, there aren't that much difference between them IMO.
For detached, it's all owner's responsible for everything like the roof, exterior paint, any minor fixes hence you pay only one HOA fee($50-$250). For attached, the HOA covers you pretty much everything exterior wise, but you pay two HOA fees ($250-$399). Of course, if you live in GP, the attached HOA will be around $400-600 per month.
But as far as I understand, it shouldn't be that much different on rates for attached and detached. If you're able to get 3.75% for detached, you should get about the same or something like 3.8% especially new Irvine homes.