We have experienced Martha Brae and are looking this time to visit the Black River.... what are peoples preferences?

Black River is a boat trip, not a raft trip. There are larger pontoon boat tours and smaller motorboat tours. I prefer the latter, since you are the only passengers and are in a smaller boat you can see and do more (or less, as you prefer).
Those smaller boats can also go right out to Pelican Bar if you want to check that out on the same trip.
The geography is different on Black River, lovely but more open in many spots. Nice views. Crocs, birds.
Which Black River? The one near Portland (NorthEast) of the one in the South with the Safari excursions?
I wasn't aware that there was a Black River in Portland? But from Lucea I'd assume the one on the south coast.
Very diff excursions! I like both for what they offer. Martha Brae is a chill vibe down a river. Black RIver if you start in the town of Black River is historical quaint town-you see people bathing at the riverbed; take the boat and see cros and I saw dolphins on the way to the Pelican Bar..a bar on a sand barge in the middle of the sea!
Martha Brae and the Black River are on different coast...where are you staying?
PEACE!
Possibly staying in Lucea (on Lucea Forum). In that case, Black River is a longer trip, but the more interesting in my opinion. Agree with Ohliz (yet again), the small fishing boats are a better option than the pontoons.
Hedo: Are you serious? Have you ever heard of a tourist taking a trip to Black River near (in?) Portland?
Yes we are staying at Grand Palladium in Lucea, we loved the genteel nature of Martha Brae last time we stayed. The Black River is different and looks great and from the comments is amazing so i think we may just go with that as it is different from what we have previously experienced.
Thank you xx