As mentioned, it depends what you mean by "better". But the real answer is simple--you have to do what your instructor makes you do. Some give a choice to each person, some let the class vote, some just say this or that. Some try to keep strict monitoring on the exact number of laps done (how do you do this with 10 people all at once....?). Some get a good idea of how many laps and an idea of who really sucks in the water. Some use the "honor system" in lap counting. The 200 unassisted means you have to make it to 200 yds. (mtrs.). Stroke doesn't matter, so it turns out for many as "gutting it out on brute strength" rather than having any kind of technically sound swim stroke. Not sure what that proves, as even with a proper stroke, swimming is but a distant cousin to scuba IMO. The 300 m/f/s is a test in leg strength (more related to scuba) and snorkeling skills, which helps some immensely when it comes to scuba airway control/mask skills. The 300 IMO is also WAY easier, except for the accomplished swimmer, or for someone who has never snorkeled. I've always been curious as to why arms aren't allowed to be used on the m/f/s300. If you were going to swim to rescue someone with m/f/s you would surely use your arms when doing the crawl. I guess it's because you should NEVER use arms on scuba. Not so--there are occasions, such as cramping, doing fancy stuff--never for basic swimming forward. I would imaging arm strokes are important to those with leg disabilities, but I'm not an expert. That's a lot of hot air, but like I said, it just depends on which swim the instructor makes you do.
