What GPS to buy
I'm a very enthusiastic user of the 2610. Have been using it in France and UK, riding in the countryside and in big cities, in hot sunshine, in rain and in freezing weather: no gripes.
Because Garmin has now presented the 2700 series, you can probably get the 2610 at a bargain, or will very soon.
Personally I like the 3-D-presentation too, but I wouldn't catigorise it as "necessary".
So: I would either go for the 2610 at a bargain or the 2720.
You live in the USA, and I don't know about BMW's pricing policy over there, but here in Europe BMW is way overpriced compared to Garmin units.
What is more, here in Europe you can get the 2610 with an extra unit that lets you handle zooming in and out and some other functions with your gloves on. That is an extra BMW doesn't offer (at least not with the zooming)
I'll attach a picture of my setup to show it.