I have no experience of the BR, but my BC20 uses a Rocna 6 with 10m of 6mm chain and a further 25m of anchor plait. This was originally purchased for my Drascombe Coaster. On both boats it has served me well for a good 10 years over here on the east coast with its thick mud. It also transferred well to other locations, such as the south west.
The upsides of this are extremely secure and reliable holding - which is even more important since I spend many nights at anchor each year - mostly manageable retrieval - when it gets stuck, it is usually sufficient to use my weight to rock the boat so that it can act as a lever to yank the anchor clear.
The potential downsides are that it isn’t easy to stow. On both boats, the bow has a sufficiently substantial pulpit area to leave it lying on a mat on the deck where it usually stays put. I'm in the process of modifying the port side anchor locker so it will more readily accept the rode, but it isn't big enough for the anchor.
If anything, I'd say it was slightly over-sized for the coaster, but just about right for the BC. If I had a BR, I'd be considering a Rocna 4 with a good length of chain. I think the chain length is probably just as, if not more important than the anchor size.
