Gengisgame said:
Better if it costs money
With free 2 play you will either end up spending a lot more money to access all characters to make up the costs of those that don't spend money or spend money to keep up with the competition if spending gives access to something.
If you aren't going to spend money then your opinion doesn't matter.
As mentioned in the OP: there's other ways to make money with F2P titles...namely skins and other cosmetics. Gamers have proven time and time again that they're more than happy to shell out the cash just so their characters can wear shiny new hats. Selling cosmetics has worked fine for other games, so there's no need for a pay-to-win model to be implemented.
Also: Blizzard has already confirmed that all characters will be available from the start, as one of the key mechanics of the game is being able to switch your character in the middle of a match, so they've already ruled out the possibility of having to buy characters.
As for TF2: It doesn't matter if it wasn't free originally...it's free now. The comparison is between what Overwatch will be at it's launch and TF2 as it is today. And indeed TF2 is older than the crust on my underwear...and yet it still has a substantial player base.
http://steamcharts.com/app/440
Now Overwatch will, of course, do well regardless of if it's F2P or comes with a $60 price tag...but will it be able to last or will it go the way of Titanfall and Evolve and fade into obscurity? All I'm saying is that considering recent trends I can only imagine that it would do better if it was F2P, or at the very least at a cheaper price.