Those that fit you well. The nose bridge and the width of the frame should fit your head properly: not too tight.
Of course there are some brands that have high-tech flexible hinges/temples that make them more comfortable. For instance, Alain Mikli/STARCK+ can be more comfortable for some people for this reason. Lindberg is also comfortable but extremely overpriced.
Actually, it depends on your liking. It has noting to do with the eyeglasses brand. It is something to do with the material of the frames or the weight of the eyeglasses. Most importantly, the prescription should be correct.
Comfort is an individual thing, I don't think that any single brand is the most comfortable, you really have to go and try them on and see which best feels most comfortable for you. Remember, everyone has different face shape, nose ridge width, distance between the eyes. so it's difficult that a brand that is comfortable for everyone. However, many of the great brands do try to make their glasses as comfortable as possible by making them of higher-quality materials and improving their design. Try checking out a eyeglasses store that sells brands, like firmoo.com and see what they have to offer. I bought my last pair there, I was very pleased with it.