I haven't tried gaia.com herbs, so I can't comment on that company. If I don't know a lot about the people producing the herbs and their methods, I don't buy them.
My understanding is that the Dr. C. herb company is using cheap imported herbs, which I understand to have been irradiated. It's not just the formula, it's the source of the herbs, how they were prepared, etc. When I returned them, within days of buying, they charged me an exorbitant restocking fee, even though they were unopened and I paid return shipping. I'll never buy from them again and their price for the "School of Natural Healing" book is ridiculous - nearly $100 if I recall correctly.
Sadly, Dr. Christopher's noble legacy has been corrupted, his books edited, formulas in book changed, actual formulas sold changed, etc. It appears to be all about money now, not true healing.
Over the years, I've used many supplements and herbs and have been scammed many times. At this time, the only herbs I'm using are the ones made by MH at Barefoot Herbalist. I've read most of his newsletters and many, many of the posts he's made on his forum. His herbs really pack a punch. I feel the effects (increased circulation, etc.) immediately after ingesting them. They have done wonders for my digestive/elimination system; his LBB really rocks. I love the Longevity Spices and Adult Dewormer and many others too. I've stocked up on MH's herbs because I think the day is soon coming when we won't be able to buy quality herbs from small businesses anymore.
I also use therapeutic-grade essential oils from one source that I think is better than the rest.
I've been around the block a few times, self-experimenting for years, wasted money on junk many times, etc. I'm just one more poster on the internet, no need to believe me or anyone else, but you'll know what rings true for you.