Star Trek RPGs use life path character creation; players go step-by-step through their characters' lives, working out what skills they received before starting play. The first Star Trek RPG, from FASA, set the standard, so other designers kept to it. LUG broke the process down by having players choose species, early life, life at Starfleet Academy, the cadet cruise, and one or more tours of duty. Starting rank above Ensign has to be purchased. Positions like department head and ship captain also have to be purchased, with larger ships requiring more points to get the advantages, thus requiring more tours of duty. LUGTrek seems to encourage characters like those seen in the TNG episode, "Lower Decks".
ModTrek, though, takes a different approach. The default appears to be senior officers of a starship, so there's no need to purchase any advantages to reflect rank or position. In fact, it is possible to have players playing Captain Picard and Ensign Ro without too much of a skill difference. The rookie officer fresh from the Academy can be played alongside the grizzled veteran explorer and both characters will still shine.
The Vulcan engineer worked out well with both systems. The LUGTrek engineer isn't on the same level as Scotty, Geordi, B'Elanna, or O'Brien, but has the potential to get there. The Vulcan is more specialized, but should improve with experience and experience point. The ModTrek version, though, is close to the engineers seen on screen. The Vulcan is still inexperienced, but will be able to keep the ship's engines going in a crisis. Scotty may have "Miracle worker" as a value, giving him the edge.
ModTrek's chargen is faster. There's not as much to track. The skills are broad, based on department. LUGTrek breaks things down far more, including different types of engineering and sciences. Which works better? That depends on style of game play. ModTrek supports getting the players in command without bogging down in minutiae, but there are players who enjoy that level of detail. Your mileage may vary. I like both for different reasons.
Friday, Mecha Academy begins.
Also Friday, over at Psycho Drive-In, The Dresden Files.
Saturday, over at The Seventh Sanctum, The Pragmatic Adaptation.