Hmmmm.... difficult question. Personally, I would say go for the misty first, just because it's a bit more comfortable (I think anyway) for a person trying their first spinning inverts. You should work on front flips a lot, and then just throw on shoulder down hard and do a little roll like you're rolling over the top of a table (visit freeskionline, they have an awesome article about it).
If you are good at backflips, then the rodeo is actually EASIER to land than a misty, but there's more danger involved and more balls, too.
'The road of excess leads to the palace of wisdom.' -Jim Morrison