Elle, my internet was down all afternoon and I didn't see this thread until last night. When I tried to comment, I was kicked off again, argh!
First of all, thanks for starting this PSA. The fit of the Brooks Brothers coats looks so good on you has me questioning my size. I wish there had been a size down for me to try on just to make sure it was indeed too small for layering over a blazer. They had a coat 2 sizes down, but I didn't even want to tempt myself. I knew it would look great over just a shirt, but was afraid I'd go and buy another super-fitted coat that I couldn't get anything under!
You have some tough decisions to make girl! First of all, it amazes me how close the BB come to the Burberry. Second, the Burberry does looks better fitting, and I'm sure that once you've had one on, you will never forget what that kind of fit and quality feel like. The casual observer may not be able to tell the difference between the two, you will be able to tell.
You could buy the light Burberry and then for little more than the price of a cleaning/reproofing you could have a navy BB as a sort of insurance policy, something to pull out when your activities could threaten the lighter coat. But then you have to ask yourself if it's worth it to have a Burberry trench that you kind of 'save'. I will be interested to see what your DH thinks about all this, and how wonderful that he is such a fan of quality, win-win!
You have to know that it was your first trench pictures that started me hankering for one (well it's been on my level 3 shopping list). You looked so mysterious and glamorous, all at the same time. Whatever you decide, I hope you wear and enjoy the coat you end up with. You were made to wear a trench coat!