The finish on any of the colored versions will be similar. It doesn't matter if you go with the red, blue, black, gray... Honestly, aside from paladium or platinum, it's just going to come down to a color preference. I know that the red, black and blue (as well as some of the higher end versions) come with a chrome grip section. The stainless version comes with a black plastic (almost slightly rubberized) grip section which I find more comfortable, personally. You can buy this part from Lamy and add it to any pen so if you hated the chrome, you could always switch later.
Pay attention to the nibs... That's where the real difference comes in. The ~$80USD Studios come with a standard Lamy Steel Nib (same as the one on the Safari/Al-Star, Nexx, etc.). The ~$160USD Studios come with a Gold Nib (sort of a two-tone nib). I've never used one, but they are apparently very nice nibs with just a tiny amount of variation (notice I didn't say "flex"). I had a Lamy gold nib in the Lamy 2000 that I had and it was wonderful. I actually really miss it and hope to pick up another one some day.
If I were going to buy another Studio (I sold mine because I just felt like it was a glorified Safari/Al-Star), I'd get one with a gold nib as it would definitely be set apart from the rest of the cheaper pens in Lamy's lineup (not that they aren't as good, it's just that they ARE as good and it's a waste of money to buy a Studio with that nib when you can get 3 Safaris for the price of the base model and 6 Safaris for the price of the Palladium model... We won't talk about the platinum one... ).
Hope this is helpful.
No, that's not blood. That's Noodler's Antietam.