Reception and battery life on both phones are exceptional.
No, you won't need any special equipment to play MP3's. All you need to do is transfer your music to the phone and you can start to listen to them via the Walkman application.
No, you won't get charged for using the FM radio, it's not streaming radio.
I've had just about every Walkman that was released up till last year. Also, every Sony Ericsson that has had 850Mhz I've used. Get the W300i because of the said stuff, and expandable memory. The Z520a is just a mid range flip phone...pretty much like a Motorola V600. Plus, if you're used to opening flip phones on Motos with one hand because of the spring assist, you'll adjust to the W300i very quickly because it has that. The Z520a doesn't, but it clicks to the 2 positions...very sturdy. Another thing, you might get annoyed with the Z520a because the dedicated camera on the side is very sensitive, and you'll be beating your head why you've taken about 50 pictures either when in your bag or pocket, or while in use.
You'll love the UI because it's so simple to use, and very responsive as opposed to Motorolas and Samsungs. The only thing I see that Motorolas have over other brands is that they're "hacked" easily.
