Both are offline HTML readers for Palm, AvantGo (https://www.avantgo.com) is commercial and you have some things like channels which you subscribe to …
AvantGo has the advantage of having the basics of Forms – where values are stored and submitted to the web server on the next sync – this is the feature which makes things like PocketLJ – the Palm based client for Live Journal work !!
But I prefer to use Plucker (https://plucker.gnu-designs.com) the reasons may be very specific to my case – I use web clippings for reading FreshMeat and Linux Today both of which I read when I am at the clinic. Plucker offers a very nice feature which allows me to copy the URL which I have tapped BUT is not on my palm to a memo – this can be edited and used from the PC for further reading. AvantGo just offers an irritating error box in the same situation. AvantGo also imposes limits on download – I have never been able to get the complete daily Freshmeat page using AvantGo. Besides using plucker I can also use sites which are on my local network (now why would I want to do that 😉
Plucker also has a better looking UI, and last but not the least it is Open source
Also in my re-search into the world of palm computing I found two very good resources php-pdb (https://php-pdb.sourceforge.net) – a set of modules which allow you to read and write Palm docs and databases, now palm enabling my PHP apps is child’s play, and also the specs for the various file formats used by Palm, forgot the URL ;-(