I think something closer to a MilSim type scenario is preferable for one long match to showcase the tactical side of airsoft, but it's also important to include some shorter, more casual games, as longer games can get quite tedious, especially to people who may only be there to have a good time with their mates.
What I'd really like to see (more than game format changes) is simply a bigger emphasis on teamwork and tactics. For example, give the teams five minutes or so before a MilSim game to actually sit down and talk about who is going to do what and how they're doing it, maybe using diagrams and maps, etc. I see so many new players (I was guilty of this) end up on their own because multiple groups on the same team were all just doing their own thing. Obviously this would really only work for longer games, as it would be tedious to do it for every little game, but I think it would be really good to get them thinking a little and highlight the team aspect, as it really is a team sport.