First off, I played paintball for 5 years, woods and speed. First strike is nothing new and people have been talking about how it will change the industry when I got into it. 7 years later and not very many people use first strike, wanna know why? They cost almost a $1 a ball and a lot of fields don't allow you to bring your own. Mag fed and limited ammo are great, I use to run scenarios at our local field, problem was most people want to run high capacity hoppers with high rates of fire, which makes for a very small player base. And really tough for guys to compete with mags.
Since I started Airsoft 3 years ago, these are my observations. The cost of 4000 BB's is $30, the cost of 2000 paintballs BYOB is $40-60 depending on how good a ball you would like to use, and first strike well that's outrageous. I play once a week and that bag of BB's lasts for a month, the box of balls would last me one day out, sometimes two if I was being conservative. So ammo is more costly in paintball for me.
I've found that most airsoft players are 18+ and the people I've been fortunate enough to run with generally play in organized groups, which works well if you like strategy and team work. Get out and play, be honourable, approachable and respectful and you will meet all kinds of great players. There are a number of semi private fields that cater to more mature players, so no birthday, bachelor parties, school trips or 12 year olds to detract from the game.
A middle of the road gun, good set of camo, goggles, gloves, mag holder and mid cap mags will run you less than a similar paintball set up, since you said you don't want to buy all the gear and dress up like a soldier. Once you've been bitten by the bug though, look out, all the gadgets and gear will end up getting pricey, it's more of an addiction.
Hope this helps a bit, I know there will be other replies with far more knowledge and experience
Either one you choose they are both a hell of a lot of fun!