Playing like a 46mm watch, the Seiko SBBN017 is my favorite watch ever, my grail watch, the watch that has compelled me to sell dozens of my watches and streamline my collection to eleven.
At a grand, plus an aftermarket Super Engineer II bracelet, it's not cheap. I was happy to sell an equal amount in fashion watches (goodbye, Las Vegas) to essentially trade for the Tuna.
At $245, the second generation Black Monster Seiko SRP307 is in my opinion the best watch for the money. It doesn't play much smaller than the Tuna, maybe 3mm in case size.
Both have professional grade lume. Both are keepers.
There are some differences. The Tuna has a 5-year quartz battery; the Monster has a self-winding, hacking automatic movement.
I love them both. If I had to, I could be happy with just 3 watches, the two featured here and my Seiko Sumo.