Yes, I have but I cannot tell the difference so I usually buy whichever is the cheapest AND smells the nicest.
I like mangoes however am not very good at cutting them, and seem to end up throwing a lot away.
The most popular ones here are I think Kensington Price.
Yes, but I couldn't tell you which varieties I've tried. At least two, but some look so similar it is hard to tell the difference. I was once given an Indian mango which was narrow, long, and orange; it was very aromatic, and I didn't like the taste. The ones I usually get are fatter and rounder, green with a bit of red on the skin.