I thought SampleTank 3 let you layer, split and multi now so you can create your own multi's like kontakt.
ST3 product page - "Want to combine an Acoustic Bass with a Vibraphone? It's a breeze. Just assign whatever Parts you'd like to the same MIDI channel. It's just as simple to split your keyboard to play multiple instruments"
ST3 has macros' kontakt has scripts, st3 has effects, kontakt has effects,.
I just think they are more similar now then st2.5 was.