I would agree that the 'hold in one hand' size of a PDA is a big plus. You need to be able to cave with the device in your hand, and unless you only survey large walking passages with flat floors you will appreciate something that you can climb around the cave while holding in one hand. Also makes packing the device for transportation through crawls and awkward entrance series much easier. I am often surveying 3 hours from an entrance and having a light weight compact kit means it always gets taken on exploration trips in case we make a break through. So we often leave the cave with data on the trip where a discovery was made.
Footleg