if I could make it to their stand each week why would I need to buy a pre-made box
I can't really speak to any of the specific CSAs you mentioned, but from working on a CSA farm, I can address the above! One thing I like about the CSA model is that you're making a financial contribution to the farm at the beginning of the season and taking on some of the risk - whereas if they rely on just market sales, they have to come up with other money to start the season, for seeds, employees, equipment, etc, and they don't know how many customers they'll have. So, it's nice for farms.
But I've also been a CSA member, and I liked having the box because it pushed me to try things I wouldn't always buy or needed to use up, so I got a little more creative cooking-wise. You also get things right when they're the best. And it's usually a better value, you'd end up spending more getting the exact same items at the farmers market, even from the same farm, because it's more cost-effective to do boxes - since they know how many members they have, they just pick what they need, and know it's going to get taken, whereas they might come back from market with unsold veggies, and have to factor that in to cost.
One last thing - since you're taking on some of the risk with a CSA membership, you might get less of something if it doesn't do well, but if they have a great crop of something one year, you'll usually benefit from that too, and get more.
Wow, I have opinions about this! But I think it's only a good option if you don't travel too much in the summer and you enjoy cooking/have time to cook several nights a week at least. That wasn't the case for me last summer, so I just stuck to the farmers market.