I was struggling with this very same question and I settled on the 100 2.8L Macro IS. It opens up a lot more versatility in my kit than the 85mm 1.2, and focusing is a ton faster. It doubles as a great portrait lens, and can help me get fantastic detail shots (wedding and newborn portrait photography). You'll need both eventually, and you can get more done with the 100 than with the 85.