I'm not sure if you're considering the 50-135 vs the 70 vs the 100 Macro, or 50-135 vs 70 and 100?
If the main interest is in doing portrait, I would lean more toward the 70, because you said you liked compactness and build of the Ltds. The 70 would also complement the 15, 20-40 and the KP perfectly (the KP was born for the DA limited). It's exactly my current setup (plus some other lenses due to LBA
) also, for portrait, 100 would be a bit too long for me.
Not that the 50-135 isn't a great portrait lens. It is. But it's an entirely different beast, and it's bulkiness is entirely different than the limited collection.