I'd go Pilot 823. One could say that I already did. I tried two Sailor 1911 w/ Medium nibs and it just didn't connect, the nib didn't cut the mustard with me and how I write. I've been extraordinarily happy with the Pilot 823 though, and try as I may I've not been able to find anything I don't like.
The black one is translucent in a nice way. When it's full, you wouldn't know it's translucent, but it's easy to tell how much ink is left when it starts to go down. Originally, I was set on getting a brown one, but an opportunity arose to try out and buy a black one and I couldn't be happier with it. I've not seen a brown one in person, but from what I've read, they're more transparent than the black one. There is also a completely clear 823.
In some ways, it isn't a very different pen. But then again, I think most pens aren't all that different in the end so YMMV. If you've the money and the interest, go for it! Sell the one you don't like if they're too similar.

They are similar in that they're both great writers, terrific tools and not novelty or specialized pens.
I've one with a broad nib, and it's line is at what I'd define as what a broad should be. Some western mediums are about the same size, but only the widest and wettest. That is, don't apply the usual Japanese rule of B (jp) = M (eu).
Aaron