Some things to watch out for on an Evo X the main one being the AYC pump. Somehow Mitsubishi managed to make them even more unreliable than the older cars, new they are £2.5K but there are alternatives to paying that much.
They need regular oil changes and there are a lot of badly modified ones around that can spell disaster for the engines, also as Dan says no way they will be better on fuel than a Z.
Saying that they are great fun to drive and a bit better inside than the older models.