Really depends what you call "best" I voted Ackies because they seem to be the best beginner monitor, haven't actually kept any myself yet. Having a hard time finding them at a decent price and most of my money is in balls right now.
My first monitor was a Savannah that was dumped on me a couple years ago. Great experience, but i didn't fall in love with them. He found a home in TX. Later I went for a CB pair in a trade, the female went to a breeder that really wanted her and another went to a friend that really loves "nibbler"
For me, my "best" monitor is the Nile. I just love the way they look, move and behave. I like knowing that if they are acting nasty, they are healthy, lol. I plenty of 'cuddly' creatures and knowledge to keep them for years. Had them for a month and are 30 grams fatter and 3-4" bigger than when i got them from the jobber.
I have some experience with B&W tegus and I love them also, I plan on getting some more when I have the space. I consider them the "best" for handable and interactive monitor. But there are many I have not kept yet.