This might sound a bit daft, but I think Pato would be the better deal.
First off, Kaka is 26 and by the time he reached the end of his contract or was here for several years, theres no way we'd make half the amount back we reported to be paying for him (£73.5m).
Pato for £30m for me is the better option. Not only do we save £40m+, but theres the likelihood we could sell him for a profit down the line. If we're to be looking after our finances this seems the logical choice.