I would definitely say you are correct about genuine watches. I would suspect that since these are rep forums, the vast majority of folks are looking for reps. Here they are looking for modded/franken watches, on the others mostly out the box reps, but occasionally a modded, but I have never seen franken watches of the caliber here on the other forums.
AFA genuine, I wouldn't waste my time posting a gen here, just not the right buyer market. I tend to use WatchUseek primarily, sometimes TZ. TZ has a lot more "Shoppers" but more "tire kickers" as well. If I were selling a watch that had a strong forum on WUS, that's where I would list it. Forums like Doxa, MKII. Ocean7, etc. that have official forums attract more people who are visiting the forums and then go to the sales forum looking for a watch. If I were selling something more unique, like a a Ulysse Nardin, Chronoswiss, IWC, etc. I would probably list them on TZ, as they have more traffic and sell more of the other brands. WUS lists tons of Seikos, so you wouldn't be wrong to list it there. Don't know about the Trazer, but why not, give it a shot, you never know.