I have noticed a monumental difference in the software available on the Palm platform compared to the PocketPC. I think this difference is best summarized by noting that Palm has the breadth and PocketPC has the depth in the software solution space.
I have to say that I have been impressed with the variety of apps available for my Palm. I get the impression that there are more Palm developers out there, but that the platform doesn't easily lend itself to feature rich applications. Perhaps the most obvious application that illustrates this limitation is Adobe Reader for Palm. This has got to be one of the most disappointing downloads on the internet. The presentation, features, and usability are all light years behind the same title for PocketPC. I personally think this is probably due to Palm’s concern over providing backward compatibility with previous models. Sure, you can find some little app that will track your pets' birthdays that will work on your brand new T5 and your neighbor's ten year old Palm Professional, but chances are it is going to look horrible on both.
On your PocketPC however, it will be harder to find those cool little obscure apps (and they're more likely to be shareware than freeware) but what is available is often more appealing and feature-rich. For example, if you want to expand the basic PIM functionality on your PDA, you may look at Pocket Informant for the PocketPC or Agendus for the Palm. Having used both, I can say that Pocket Informant has more functionality and considerably more eye candy than it's Palm equivalent. There are exceptions of course. For example, there is a fantastic freeware calculator for the Palm called Easy Calc that I absolutely love. I searched high and low for an equivalent application in my price range for my PocketPC and never found anything that was even close. My general observation has been that exceptions aside, PocketPC applications are generally more appealing.
All of this having been said, I am not ready to declare a champion either way. The jury is definitely still out on the issue, and I will try to post more on this subject at another time.