I'd go for the 630. Simply because it has some better stats than the 530. The 635 is only worth it if you actually have a 4G subscription.
About the maps, Lumia Maps is awesome. You can download the maps you want to use offline, for free, and even have a very good turn-by-turn navigation all built in, using the same maps, all without having to use your data connection (if you download them using wifi, naturally).
I tried to use the google map offline once, on my android tablet, I never got it to work, so I can't describe the difference (except my Lumia one works, and the google one didn't
)