Unfortunately most fish oils and krill oils are similar in that one manufacturer produces the oil for many vendors and brands, there are very few that are 100% pure. In fact Neptune krill which is the largest manufacturer of krill oils supplements is branded on many bottles.
I personally have taken Mercola krill oil and Everest nutrition. I like everest nutrition because it ships directly from them as used be the same from Dr Mercola. Recently I have seen other companies such as Amazon selling Mercola krill oil which does not give me complete confidence in their product.
I have used both and once when I ordered some capsules from Mercola a few of the capsules had broken or had dissolved leaking the oil on the rest of the capsules. I called Mercola and they did replace the bottle wit no hassle.
Unless you are allergic to fish oil I have never had an adverse reaction from either brands and have nothing but good to say about them, in fact I have teo young children who take one capsule a day and have also never had a bad reaction from either brand.
Here is a good comparison of the two products mercola vs Everest nutrition.