It's a somewhat complicated, fairly political question but here's a few thoughts...
One contributor here went with Distant Horizons and based on what she posted when she returned (lots of misinformation and outright lies/propaganda fed to them) I certainly didn't respect their tour guide's motives.
I was also witness to a Distant Horizon's interaction in a restaurant in Trinidad recently and the agenda was, quite frankly, laughable. Even the accommodation options are designed to keep the group safely sequestered from the so-called "real" Cuba. Lastly, the cost is ridiculous (compared to a properly research and planned independent trip.)
That said, if you're a nervous traveller and don't wish to visit Cuba illegally then one of these tours is your only option.
Another option for you to consider is to travel illegally to Cuba. The legal repercussions for tourist travel are non existent now and have been for several years. Have a read through Reply #1 here:
http://www.tripadvisor.ca/ShowTopic-g147270-i91-k4402971-US_travel_experiences_to_Havana-Cuba.html
No matter how you decide to handle it I'm sure you'll have an interesting time.
Good luck.
Cheers,
Terry