Interesting...
So the majority seem to have a slight preference for the 10, but a significant minority (including Angie) says 8. It gets more even if we're talking about only wearing it unbuttoned. I'm still undecided. (For the record, I did not buy either yesterday, I am going to order it online once I decide, and probably wait for a ubiquitous BR coupon to appear. It no longer seems to be a BR pick so I think coupons might work on it?)
So the thing is, the 8 fits better in the shoulder, lower arm, and waist, but (as per today's blog post) the upper arm is very slightly snug. It doesn't hamper movement but does bunch a little with the long sleeved shirt under it. The 10 is slightly big in the shoulder (but doesn't droop or anything) and I find the lower arm a little too roomy. On the other hand, the fit over the bicep is better. It's also a little boxier and I do prefer the more fitted shape of the 8. (I feel that a lot of blazers tend to look a little bit too big for me even when they're the right size because they're not fitted enough.... )
You all are right that I'll probably never button it. I'm not a buttoned blazer type, and frankly if I need to go super formal for something I'd wear the much more formal black blazer from my suit.
Janet, I probably wouldn't wear thick layers under this blazer. This is a medium weight shirt and I wouldn't go much heavier. I might add a cami under or a sweater vest over but it wouldn't impact the arm fit, which is the tight point on the 8. I don't like the feel of layering thick sleeves (like on a sweater) under woven blazers so wouldn't do it anyway.
Ack. Still undecided. Maybe I need to order both and try them on with a bunch of things?