You could probably search the forums for similar questions but it comes down to a matter of preference. Our software is available on a try-before-you-buy basis so you can get a device and test drive our software prior to purchasing a license. Most devices offer a return period as well.
I have them both and they both look and act basically the same. The palm OS I used on the treo and it had one bit of functionality I liked because of my treo's d-pad. When you enter your leg times you just had to tap on the dashes and use the d-pad up/down to adjust them. My new phone (TP2) doesn't have the old d-pad so I have to highlight the time and manually enter it using the numbers on the keyboard. If your thinking of running the palmOS version with WebOS on the Pre, just run it in Classic. It works fine. Just be sure to close Classic when your done putting your times in because it a real memory pig. I had the Pre for a couple of weeks and took it back.