I can definitely tell a difference between Pepsi and Coca-Cola. I grew up drinking Coke, but once I started working I switched to Pepsi, and I prefer Pepsi now. Coke just feels really thick, leaving a film in my mouth, and has a weird aftertaste.
The other soda I can taste a difference on is Crush versus Fanta. I prefer Crush's orange over Fanta's. Again, Fanta (being a Coke product) just has a weird aftertaste, and the last time I drank some I felt sick. Crush is just more refreshing.
There's really no difference with the clear sodas, so I drink whatever I can get for those. (Although a local soda company makes the best lemon-lime soda I have ever had, and so I get that that when I want that flavor.) Probably because those aren't my sodas of choice. Pepsi is, so that's why I can recognize the taste of that more.