When comparing ScanSat vs Mechjeb, the Slant community recommends ScanSat for most people. In the question“What are the best Kerbal Space Program mods?” ScanSat is ranked 6th while Mechjeb is ranked 8th. The most important reason people chose ScanSat is:
You can create detailed maps of every planet.
Ranked in these QuestionsQuestion Ranking
Pros
Pro Create maps
You can create detailed maps of every planet.
Pro Helps with landing the spacecraft
You can use ScanSat to determine the slope of the surface you're landing on and avoid hills and other obstacles.
Pro Much better than the stock scanning system.
The stock resource scanning feature finishes instantly, while ScanSat functions over a long period of time and the orbits you're in, like scanning satellites do IRL.
Pro Science boost
Provides a little extra science to help you in your career and science mode games- but you'll have to work for it!
Pro Realistic
Real rockets use autopilot, so this is more realistic and not cheating.
Pro Automates some tasks, while still keeping you in charge
Even if you scoff at the idea of having the computer do maneuvers for you, there are still numerous other useful tools for manual flight.
Pro Very nice for simulations and beginners
Pro Has autopilot features
Cons
Con Some users experience performance losses
This is only true when the window is open, it shouldn't affect the rest of the game.