If you Google paint reviews and look on YouTube you'll find a lot of commentary. A great deal contradicts, which should tell you that there is less difference than some folk might want you to think.
I haven't painted myself for years, but having spent decades dealing with painters of every level, including many professionals, I'd say that outside GW's navel-staring bubble, nearly everyone who paints does so with a mix of different companies' products. I'd also say that the majority of professional painters I've heard comments from use Vallejo for the bulk of their paint, and cherry pick particular things from outside. Not always true, but very common.
Remember also that the particular qualities of a given paint range may be perfect for one style of painting, and not suit a different style at all. So when you watch a review, also look at the way that painter works, to judge whether their comments are relevant for you. For example, if a painter uses airbrush or thin washes then they will find thick paints need a lot of thinning to suit them. If they drybrush a lot then thin paints will be an issue...
Hope that helps.