It's surprising how much lighter the 17" can get when you remove the battery from it, it's a good bit heavier than my 15" batteries. Although you'd want to keep the battery in if it had an life in it left, my 17" battery was in great condition, 30 cycles, charged to 100% and then after a few days crazily expanded so much that it was a huge fire hazard. I don't have any photos of it as I've safely recycled it but it looked similar to this:One of the key physical differences I noted between my PB and my MBP is that although both are 17", the MBP is slightly wider than the PB. But the PB is slightly deeper (front of PB to rear of PB) than the MBP.
Of course, the MBP is also LIGHTER.