If you already have Miroslav, there really is no point in re-purchasing the same samples for Kontakt. They sound exactly the same. (Yeh, I got suckered into buying the Infinite Player versions.) And you won't get everything from Miroslav, just selected patches.
The only benefit is that you'll be running 64-bit Kontakt, which means you can load up more patches at once. But remember that one of the great advantages of Miroslav is that the libraries aren't very big, so you can easily load 16 Miroslav libraries even in 32-bit land.
I'd also add that some of the built-in effects in SampleTank are better than their Kontakt equivalents, reverb in particular. I run Miroslav within SampleTank and often mix 'n match Miro patches with ST patches.