$16.99?? Wow...where? I gotta know.
Try downloading the demo at www.download.com
for all three - type "Star Wars" into the search thingy, and you'll get to downloads of all three.
At $16.99, jeez, might as well get all 3. They're 3 entirely different styles of games, so it's difficult to recommend one. Alliance is space combat, Racer is pure racing, TPM is action/adventure.