I think the "best for the money" pda is primarily an issue of what features you want. When I started looking for a pda for external ballistics use, I started looking for a palm with OS 3.5 and at least 2MB of memory. I also wanted a backlit screen for night use, and rechargable battery. These are what is required for exbal, considered by most to be the best program for field use.
What I decided was best for me was a Palm Vx with 3.5OS, and 8mb of memory, enough memory for al three of my PDA based ballistics programs, a reloading cost calculator, and a whole mess of games for my girlfriend to play while im shooting. A couple of palm III variants would have fit the bill, but The price was right, and the extra memory comes in handy. The program I am using most is actually a shareware program... free to use and distribute.
As for computer based programs, I use the sierra I5 program most. Very easy to use, and gives accurate info in most of the instances ive tried.
Im not aware of a program that is compatable with both interfaces.
Hopefully others will comment who are more knowlegable than myself on this matter.
In my opinion, its really a question of what features you want more than anything else. Palm III variants with OS 3.5 and 2mb or memory can be had for $25-$35 on ebay if youre patient.