I have really thought about the difference between the Duggars and the Gosselins, since I usually hold all people to the same standard... and for some reason, what the Duggars do just doesn't bother me, yet the Gosselins make me insane. I have really thought about why that is since I stopped watching the Gosselins around season 2 and I still love watching the Duggars. These are the reasons I see a difference: (besides the obvious which you stated is that they are nicer and pleasant to watch instead of how the Gosselins were like nails on a chalkboard)
1. The Duggars have proven they are more than capable of providing for their children without the TV show. They have never taken handouts. Althought the cameras are there, no one has quit their job. THey still have their business and cater etc. They haven't upgraded their lifestyle because of the check coming in from TLC. They have remanin the same. (THey do have a nicer house, but they were dong that on their own anyway, the show just made them be able to finish it faster) - they still had a place to live while they were building it. If the show ended tomorrow, their lives wouldn't change much. Dad would still have his business...Josh would still sell cars, Mom and girls would still cater. The Gosselins were NEVER able to care for their brood on their own and took handouts before they had a show. They upgraded their lifestyle based on what income they thought their kids could provide for them.
2. Where the Gosselins focus seemed extremely self-centered and self-absorbed, and self-indulgent - I feel the Duggars focus of the show is more about evangelization, spreading the word, showing that God provides, having faith. I feel the cameras are rarely on the little ones, where the little ones were the sole source of entertainment on J&K, and J&K were voice-overs for the main part - the cameras are usually one Michele, JimBob and the much older children on the Duggars....once in a while you get a flash of a little one playing.
3. I watched J&K because the kids were cute. I watch the Duggars,because I have learned so much from Michelle about meal planning, patience, teaching the kids responsibility, organization. Jeez, organization alone! - this woman is amazing to watch in and of herself. I would still watch her if there were no kids on the show. She is better than Martha Stewart! She is real. Kate seemed like a big fake to me. She really didn't have anything there to teach, she went on and on about cooking healthy for the kids, but other than use the word "organic" a thousand times, I really never learned anyhting from her, other than she is killing the planet with paper plates. Yeah, she was organized, but it was born out of control more than anything else.
So that is the difference to me. THe Duggars have some thing to offer, to sell other than their kids. Yeah, the kids are running around in the middle of it, but I just don't get the icky, "selling the kids feel" from them. I get the more of a feeling that they are proving to the world that the Lord provides when you trust in him and put everything in his hands even the number of kids you have. Michelle is piming any books with private info. They don't have nannies, cooks, and gardeners when the filming is being done. The kid is out on the tractor mowing. The show is truly about their real life. Not just selling how the kids are cute. Then selling and promoting their divorce for ratings. Then selling info that the kids are in counseling. Then selling private letter from their mother to them. The Gosselins are just plain icky. The Duggars aren't.