It's all personal opinion. If you just want opinions, I'll tell you mine. No, I do not think the 3D mapping is worth the extra money. I don't even care for the way it looks most of the time. But that is just my opinion. Most people (that I know) think it "looks really cool", and then end up running around with the 2D maps most of the time.
Different cards will give you different coverage and features. My favorite aftermarket cards have been the Navionics HotMaps Premium (not Platinum). It's $50 cheaper ($149), and it gives me a lot of really good coverage, contours, features, etc...
However, I will say that Lowrance's mapping is getting even better all the time, and there are many times where I find myself sticking with Lowrance's Insight mapping over the aftermarket cards. With the advent of Insight Genesis Custom Maps, it's likely going to just keep getting better.
All the best,
Glenn