As a general rule, Limited Wish is *most* often used to duplicate lower-level spells.
The 300XP cost is a very small amount compared to average XP at this level (less than one-third XP gained from an encounter of CR=min.caster level with an average party size). The versatility is very useful, and can easily be a make-or-break for the character, or indeed the party. For one, you can duplicate Raise Dead if the party cleric dies. More to the point, you can be very versatile if combat, drawing exactly the right spell for the situation out of the hat.
Wish, on the other hand, is a different kettle of fish. 5000XP is never anything to be sneezed at (roughly four times XP gained from an encounter of CR=min.caster level in an average party size). It is typically used for its greater functions. Incidentally, a nice little way to cheat with Wish is instead of duplicating spells, creating magical items: scrolls with said spells inscribed (of course, this won't help you with divine and prohibited spells)