Don't get either of those. Sony and JVC are junk for car audio. You can get a low-end Pioneer or Panasonic for around that much and have much better quality.

Check Ebay for a Pioneer DEH-P3600, Panasonic CQ-C1300U (also plays MP3s), and Clarion DB345MP.

www.onlinecarstereo.com also has a nice selection of decks.