I think it is subjective. My Rosemary brushes were, to be brutally honest, rubbish, could have been a bad batch. The bristles splayed within weeks and never kept a point, only one I have left is used for liquid cement now that's what I personally thought of them. The BT do have thin handles, which I like, but after a few weeks abuse, they are still as good as when they arrived.
Better than W&N? I am not qualified to say but they are cheaper and have longer bristles than the W&N 7's that I got (one of which shed some hair when new but is ok now, the other two are ok but little used). I really like them and will use them as my brushes of choice.