Personally I like Mil-Sim, I've hosted games that had a SWAT theme, pistol only matches, etc.
I like airsoft because its tactical, no poking your head around the corner, finger fucking the trigger as fast as you can and then hiding.
As far as gear goes, I don't care. Wear jeans if thats all you've got (especially if your on the other team, you'll be easier to spot), bring a springer if thats all you can afford but have a tactical attidude when you come out, not the paintballer mentality. Lately there has been a lot of noobs wanting to hold games with 'no high caps' well I have 10 hi-caps that I use, this way I load up at the start of the day and I'm good to go for the entire day. Minimizes down time.