You can click on any item in the shops, and check the tab "Ranks". There you see what stats get improved.
Example: Light Body Armor gets +4 body and leg armor on +3. The rest of the body armors gets +5 on body and leg armor on +3. The same for boots; the very light boots get +4 leg armor on +3, the rest +5 leg armor.
Weapons are different, for armors you can generally say that very light gear gets +4 additional armor, the rest +5. A Great Sword, which is 2h, for example gets +1 Speed, +2 Thrust and +3 Swing Dmg. A 1h weapon like the Short Sword gets +1 Speed, +3 Thrust and +3 Swing Dmg.
A Horse like the Destrier gets +2 Speed, +4 Body Armor, +15 Hit Points, +2 Maneuver and +4 Charge on +3.
Just check the shops.
