Example: Storve the Fighter buys +2 magic chainmail. Chainmail gives him +6 AC, and the +2 enhancement bonus brings it to +8. Blorve the Fighter buys +2 magic finemail, which has the same cost as +2 magic chainmail. Finemail gives a +7 bonus to AC, with the enhancement bonus bringing the total to +9. Blorve the Fighter is now strictly more powerful than Storve the Fighter, who got completely shortchanged. They both go and fight in encounters of equivalent difficulty, but Storve has 1 less AC than Blorve, and he dies

Unfortunately for Storve, his DM wouldn't let him obtain the level of armor that the game and encounter design expected him to have.
~ fissionessence