As if we don't have other more important problems, but ok, I'll bite.

Exponential leveling curves have time and again proven to be the worst thing you can do in an MMO. It creates huge problems for both casual players, the economy and even hardcore players.

Look at the current top level heavy economy with 90% of all items, crafts, gathering completely useless. You can see this right now in the Materia Market. No one gives a ... about grade I-III Materia. It's not worth to even put into armor because you outlevel your gear so fast. 30/40-50 however is extremely overpriced.

That is just one example, but it applies for the whole economy. Crafters at low level can't sell their stuff they level on because no one bothers. I can go on but i think you get the idea. It's BAD.

Linear progression is the only and best solution. It's easy to balance and easy to adjust. Linear means it takes 1h to level from 1-2 as well as to level from 49-50. (The 1h is an example).

@OP: If you correct your Post, please also correct your "would of" atrocity. It's "would have" for crying out loud!