This kind of depends on how much data you need to put in there. All the units - either Palm based or PPC have decent database software availabile (either included, freeware, or shareware). If you need the database to have graphics capability then you probably want to have a PPC based system.

Both of the machines these days have some type of expansion capability (such as a compact Flash, smart media, memory stick, or even microdrive). These are a little expensive but a lot cheaper than they used to be. And getting cheaper all he time. And both types of machines have alternate input capabilities (you can buy small external keyboards for each or synchronize the data from a PC/Mac. This is probably the key to using some of these - being able to get a lot of data into the sytem.

There are some programs that will read/write Access type databases. You can take a look at some of the shareware/freeware available on http://pda.tucows.com - something like HanDBase

There is a third possibility, a sub-notebook. I think I remember Andy having one of these and you can get a used one pretty inexpensively. They are basically mini-notebooks - either like the Toshiba Libretto or a full blown one like the Vaio. Then you are using Access, or another database program to do the same thing.