I recently found out that Truxton (Tatsujin in the Japan) had a PC-Engine port in addition to the Genesis/Megadrive port I played. Unfortunately, (probably the reason why I never heard of it before) the game wasn't brought to the US TurboGrafx-16 because by the time the game was released (1992) the TurboGrafx was already dead. There's some real differences (I'll edit my post to list them) between the games which led me to wonder:
Have you played both games? Which game do you like better?
EDIT: Since the last comparison got lost after I logged back in, I'll type a short and sweet version, and later expand upon it.
Visuals:
The Genesis/Megadrive version has grittier, more detailed graphics. There is also a black bar occupying the right-most fourth of the screen displaying your score, lives, difficulty, bombs and powerups.
The PC-Engine version has brighter, more stylized graphics with brighter colors. In lieu of the black bar, the PCE version fills the entire screen showing your 1-ups, score, and bombs on the corners of the screen.
Audio:
Overall, the Genesis/Megadrive version's audio has more bass and some mild distortion. The greatest example being that nightmare-inducing ship-explosion. Both games have the same tracks, but the G/MD version's soundtrack is lower and more technical. There are more sound effects than the PCE version, every enemy and boss has a sound effect when they fire their weapons.
The PC-Engine version has the same soundtrack with the exception of a track called "Ranking". The PCE version's music is faster and more melodic. The sound effects are your standard 8-bit fare, with the exception of the weapons. The sound effect for the Power-Shot sounds like a machine gun. Very nice. The Tatsujin Beam sounds like TV static. The sound effect for the Sun-Laser sounds like the Twin Shot from the Top-View stages of Thunder Force 2. The sound effects are often reduced to small chirps and blips when you're firing your weapons. (Not enough audio channels on the PC-Engine?)
Gameplay:
The gameplay overall is mostly the same for both versions. The Genesis/Megadrive version has a couple saving graces for the difficulty. The first is the bombs. The bombs in the G/MD version fill the entire screen. The second is the Power-Shot. The third upgrade gives you two satellites that generate shields that destroy small enemies. Unfortunately, they do not block projectiles. The third is the controller having three buttons. In addition to the rapid fire, you have a single shot that comes in handy for when the stage calls for more methodical firing.
The PC-Engine version is more difficult than the Genesis/Megadrive version, but there are some advantages. As previously stated, the thrown off aspect ratio. This leaves less enemies off-screen which leads to less cheap deaths. The third upgrade of the Power-Shot in the PCE version just fires more bullets, instead of spawning those shielding satellites. The bombs don't fill the entire screen, but they do stay on screen longer, so if you manage to trap a boss in the blast radius the entire time, it'll do more damage. There is no single fire, there is only rapid fire which can lead to some frustrating deaths in some stages. (Stage 2) Gameplay wise, the PC-Engine version sticks a bit closer to the Arcade Original.
EDIT: Made a video of the three games' soundtracks being played.
http://www.youtube.com/watch?v=cIyXK-hHyXY