Just play the tutorials and test which one is doing best for you.

I always play Psi with their ability to hit bloons wherever they are, but that is just one play style. And it’s a rather expensive hero, they cost nearly twice as much as Quincy, which means you need to build another tower first and gather money and that again leads to a lower hero level.

It’s a hero that doesn’t require you to do much. Other heroes like Geraldo and Corvus need a lot more management.

The amount of Monkey Money you spent on heroes also plays a role, because that makes them cheaper, start with a higher level and level faster. And if you can’t immediately buy a hero it also matters how much Monkey Money you spent on reducing the cost of towers you wanna build first.

If you already have a hero you like to play, I’d rather get a few of the cheaper heroes, since that allows you to play more maps with fixed heroes. (dailies and contested territory)