2 VS. 3 is really minimal difference.
2 vs 6 is usually where differences come into play. I prefer two larger meals on non-fasting days rather than 6 small meals because my body will be spending more time using nutrients than storing them. When you eat a meal, your body's main focus is the storage of those incoming nutrients, fat in particular. after digestion is complete, 4-6 hrs later, your body will shift into a state that is more geared towards utilizing the nutrients consumed.....so I find its superior, in a fat-burning perspective, to eat less frequently (but still the same amount of calories), than to eat more frequently, as you give your body a chance to dip into your fat reserves (pending a caloric deficit), and not be constantly digesting and dealing with (read: storing) nutrients and cals.
your metabolism will not be slowed down with 2 larger meals a day, either. As long as you are hitting your calorie and protein goal, your metabolism will not slow, contrary to popular belief ( ie you MUST eat every 2 hrs!!!!!)
with regard to insulin levels, anything you eat to break a fast, or anything you eat in general, will raise your insulin, FYI. Insulin has many functions in the body, and is released after eating anything, be it a steak or a bag of doritos. However,chronically spiked insulin, due to excessive carbs and stress and such and poor diet are what youre really trying to avoid.