The most obvious one is Zeromus's sprite, but that isn't until the end of the game. In fact, most of the differences between FFIV easytype and FFIIus aren't until later in the game. The ones that spring to mind are:

Zeromus's battle sprite (which I already mentioned)
The ribbon absorbs elemental fire, ice and thunder
a sword (I believe mithril) was changed so that it's no longer metal
weapons placement is a little friendlier
I think there's some changes in enemies

This is all covered in the URL in the FFI-IV FAQ (FFIV: Everything You Know Is Wrong). It clears up MANY common misconceptions about the games. For example: there IS no FFIV Hardtype. However, calling it Hardtype is actually a VERY good way to distinguish it from Easytype, so don't feel like you have to stop calling it that. It's a perfectly acceptable method of reference.