For me the question that you should be asking yourself is whether a 1910 is going to fulfill your needs in a year from now. With the next version of PPC OS likely to be bigger than the current one (look at the 48 meg roms that are in the Axim and the new HPs) it is unlikely that you would be able to fully upgrade a 1910. Of course if you are not too fussed about having the latest then that might not bother you.
On using a PPC when studying law - one of the things I found most useful was a Stowaway keyboard for taking notes in Lectures (much better than lugging around a laptop and battling for a power point!). I guess both the TT and the 1910 (and other PPCs) would be fine for that. There is a very useful ebook reader called Ubook (http://www.gowerpoint.com/uBook_down_nf.html
which can read PRC, RTF and HTML and other formats as ebooks. I have found this really useful for reading notes etc and stuff downloaded from the net for study.
I guess none of that really goes to the question of which PDA, but I used a HP 568 which is about the same size as the Axim and I am looking to get an Axim advance soon. I never found the size to be an issue.