Druid Charming Spell Series Question

[Xap]

Just a quick question to more seasoned druids.

With the Druid charm animal line of spells (Befriend-Charm-Beguile-etc) is the only difference the level range at which you can Charm mobs?

For instance Befriend only works on creatures up to 24 (IIRC), charm up to 34, etc.

I'm just wondering if its beneficial to charm say a lvl 30 Rhino with Beguile or can I save some mana and use lower level Charm Animal to get the same result?