I like the Brothers Duomazov review of the TG16 version. I'm nowhere near that good of course, and can't get anywhere in the TG16 version in my limited playing of it (in emulation), but that review is accurate: The TG16/PCE Tatsujin is HARD. I have the game for Genesis, and the Genesis game is hard. I haven't finished one loop of it yet, despite some trying, but I have at least gotten a few levels in to the game. It's pretty great, once you get into it. But that TG16 version, it's just insane! The difficulty level is absolutely stratospheric, it's no comparison to the Genesis. They made the game exponentially more difficult, and it's just so insanely hard on TG16 that I can't get anywhere in it. So many bullets, that move so fast! It's just too much. The game's brutally hard enough on Genesis, why did they have to make it so many times harder? But for really good shmup players who are also masochists, it's pretty much the perfect game, isn't it. But for me... too many fast bullets, and if even one of them hits you you die and go back to the last checkpoint. It's too much to handle. Why did they make this version so crazily hard? Just to differentiate it from the Genesis version, which of course released something like three years earlier?
As for graphics and sound, the two versions each have their different styles. I'm not sure which is better. It is disappointing that on TG16 enemies don't show damage, though -- on Genesis, some enemy types have a damage state after you hurt them some (flames break out on the larger ships, and such), but on TG16 they just look the same until destroyed. That's one plus for the Genesis. It's also worth noting that as with all vertical Toaplan games, the game is fullscreen on the TG16, but runs with a large black status bar on the right side on Genesis in order to preserve the aspect ratio. I'm not sure which of those styles is better, but all of Toaplan's games keep that design split in place. Also the Genesis version has a darker color pallete than the TG16 game, which looks much brighter. As for the music, they're different remixes of the same stuff. They're both really good.
Overall I like Truxton/Tatsujin a lot. It's probably my favorite 1989 Genesis game, actually. But the Turbo version... argh, I want to like it, but it's too hard! It's just as great a game objectively, but I don't know how many people can actually handle the challenge. I know it has some hidden difficulty options, but I don't think there's any way to make it as "easy" (read: really hard) as the Genesis version is.
The second game in this series, Truxton 2/Tatsujin Oh, is probably even better than the first game. It's really too bad that its only home port is on the FM Towns...