HEADSHOTS: 85L 1.2 or 100L f/2.8 Macro IS USM?

I'm a professional headshot photographer and have been using the 85L on my 5D2 for years.  I typically shoot handheld, f/3.5 @ 1/320sec under my usual lighting setup.

I'm not really hurting for IS and am OK with the focal length of the 85L, but I rented the new 100mm Macro today for some food work and it got me thinking: I don't really use the 85L in "God mode" (wide open f/1.2) for any of the work that pays the bills around here.

So I'm wondering if the faster autofocus and the Macro capability might not be worth considering as a replacement.  Funny, I've really grown attached to the heft of the so-called "Canonball" and see the world at 85mm (a problem I know I need to correct, just admitting it's my comfort zone).

Any thoughts, gang?

—m

www.michaelcavotta.com