The PAM249's are so easy to find (over retail though) that they're a dime a dozen now if u're willing to pay the premium. The 28A is getting much more difficult to find, so I'd jump all over the 28A if I were you
Furthermore, you will then have a Radiomir and a Luminor instead of 2 Radiomir's. Best to mix up the collection a bit IMO.
Cheers,
Anthony