The Brahma has long, low rocker in both tip and tail, and it will ski very differently to your 82. The 8.5ti has a much shorter section of early rise in tip and tail; it will ski a little differently to your 82, but the difference will be less pronounced.
The Brahma will be a more playful and fun ski, will be easier to pivot and slip, and will be more versatile off piste. The 8.5ti will feel like a more serious, powerful ski, will feel a bit more 'planted' on mother earth, and will be more stable in heavy, junky snow. If you like the traditional feel of a ski that hooks up along it's entire length (like the Monster 82) the 8.5ti is the ski to choose between the two.
I have no real experience of either in bumps, so I'll leave that to others (or Dawg's reviews in the link below).
I spent a day on the 8.5ti in Whistler earlier this year, and managed to demo the Brahma last month (in a size too short for me). Conditions last month were our usual mix of cut-up, refrozen crud with the occasional patch of reasonable snow. In those conditions the Brahma simply would not settle down to the task at hand. The rockered tip/tail were only occasionally in contact with the surface of the snow, the ski felt very short, very turny and really only felt stable to me when high up on edge. They were fun, but I was happy to hand them back. For my money the 8.5ti would have been a very good ski in those same conditions. They just feel like a more substantial, stable, mature ski.
Of course, if you're flying around in a couple of inches of lovely, soft snow all the time it would be a different story.
Dawg does a great job of reviewing the Blizzard lineup in the following thread. The Brahma is essentially the Bushwacker with metal, so consider the Bonafide (which is laid up with metal) and Bushwacker reviews together to get to the Brahma.
For me (I'm a big guy) I far and away prefer the 8.5ti. I own the Head Monster iM78 (183cm) so we're coming from a similar history.
As ever your best bet is to demo each before making a choice, if you can.
Best of luck.
[edit - spelling]
Edited by sinbad7 - 9/27/13 at 5:01am