There is no single option that is best for everyone. The best fit for each person can depends on a variety of factors, and they can have different weights at different times / in different circumstances.
For one thing, great players all have a lot of knowledge and skill. But that doesn't mean they can all have similar levels of ability to convey what they know. It also matters how the student thinks and learns, and how that fits with a particular instructor's communication style.
There's also the matter of how appropriate different players' materials are in terms of fit with your game. For instance, Negreanu is a small baller. This style is a better fit for deep stacks and slow structures. So, it's not necessarily a great a fit for a lot of online tournaments, including many regular speed ones.
And as a third example (among many other possibilities), people differ greatly in their ability to change / adapt their styles / games. So, in my case, while it's still useful to learn how top-notch LAGs think and play, in practice, I'm never going to change enough to have such a style. So, I'm more likely to improve my own game by concentrating on material from trainers whose styles are closer to mine.
change instances of free poker into a link to https://www.cardschat.com/strategy/free-online-poker-game/
I have never used it so have not experienced it on a personal level but have heard good things about it, and hey there is no harm in trying 
