Couple of weeks ago someone was asking if there were any numerical data floating around for comparison of all the possible set upgrades. Lengthy discussion of priorities for guilds followed but no such data ever emerged.
So, having a very boring job in the military right now I took the time over the past couple days to make some spreadsheets for the community.
Link to the file: (file is an Excel spreadsheet)
http://files.filefront.com/Tiered_Ar.../fileinfo.html
Note that the workbook has multiple pages. The first worksheet is "Sets" and is all the data for each piece of armor for T2, T2.5 and T3 for ALL classes on one page.
Each class then has its own worksheet (color coded by class) showing the gains/losses in stats for each Tier of Armor as you move between the 3 sets.
Edit - I hate when I hit submit and forget to paste the links.
Edit - Updated link after changing the file to reflect some bad values on the Warrior T2.5 set.