Handheld PDA devices are available in many different sizes, so
another factor that you must consider when choosing which to purchase
is which PDA devices feel comfortable to you and which do not. Some
PDA devices are very tiny and difficult to handle, and some are very
large and simply aggravating to keep with you. It is important that
you choose a PDA device which feels comfortable to you, because you
are going to end up handling a lot on a daily basis. The size of your
PDA and the keyboard on your PDA are both extremely important aspects
worth considering when purchasing your PDA.
http://projectpda.com/article/344/PDA_Buyers_Guide