With flight controllers the field is so rich that is better left to the people that know most about the items...the creators. Suffice to say that the choices are varied. The processors can range plain PIC processors to full featured ARM types. Which is best? Well they all have their good points so it's more a matter of what you want to do. Questions worth considering are: Expandability, Upgrade path, Ease of configuration /programming, Support group. You can talk to any number of people and come up with an equal number of recommendations leaving you in essentially much the same position as you started.
There is no easy way around this one. We will certainly review and comment on what's out there, but you need to ultimately decide on the level of coplexity in programming and how much nuts bolts assembly that you would like to get into. Each flight controller out there inposes it's own set of demands on the buillder's knowledge and therefore level of effort required to make tihngs work.
If you are the kind of person that likes to pull something out of the garage and just go fly it, you might be better served by an off the shelf controller system like a Walkera or X-BL or LA-Heli. The Walkera stuff flies out of the box while the X-BL & L-Heli require a little preparation before they are flight ready. In any case, it's all about the device that best suits your needs (and wallet). Here is a short list of off-the-shelf and DIY Quads for you to do a little research before making a decision.
Off-the-shelf Quads & TriCopters: