Here is a link to a listing of the most common oolong tea cultivars in Taiwan:http://houdeasianart.com/download/Oolong_Species.pdf
As far as I know, the only Ti Guan Yin tea commonly grown in Taiwan is the the Muzha TGY referred to in an earlier post. It is a much more oxidized/roasted tasting oolong.
The only Taiwanese green oolong that tastes similar to an Anxi Ti Guan Yin oolong (green style) is Baozhong oolong. They both have that bright green scent and taste. The high mountain Taiwanese oolongs (Alishan, Lishan, Shan Lin Xi, Da Yu Ling) taste totally different, because they have unique and complex scent and taste that I guess comes from growing at high elevations. I prefer Taiwanese high mountain tea (gaoshan).
So if you really like the green style Chinese Ti Guan Yin, you will probably enjoy Taiwanese Baozhong (sometimes spelled Pouchong) oolong.
The different growing environment definitely creates some differences, but production techniques are going to play a large role as well. Taiwanese tea masters are going to have a different set of standards about what characteristics make a good tea, and they're going to adjust their production methods to accentuate/bring out those characteristics. The picking standards, for a start; the stem left in the Taiwanese tea probably makes a somewhat significant difference.
Every producer is going to be somewhat different, though. What I've generally noticed is that the Taiwanese wulong tends to go for a more clean, pure, round tea; fresh tea brewed right can often give me the sensation of a large pearl in the middle of my tongue with a taste that reminds you of bright, fresh green tea leaf (i.e., vegetal aspects).
Anxi tends to be a bit more warm and soft with a mouth-feel that seems to melt into the tongue, and an aroma that offers more of the "peacock display" of floral notes that is typical of TGY.
Overall I would say that the Taiwanese tend to go for complexity in how the tea changes from smell, to taste, to finish, to aftertaste (with each being relatively humble), while the Chinese like a little more up-front complexity. That's not to say that they don't both have these characteristics; it's just what each seem to accentuate a bit more.
Really, though, I've gotten a lot of different TGY over the years (I probably have a dozen on my shelf now; mostly darker roast), and they're probably all equally different.