Convection ovens and microwave ovens do have some similarities, but the way each appliance cooks is very different than the other. For example, conventional microwaves emit microwaves that are capable of passing through glass and plastic containers to cook food. A convection oven, on the other hand, cooks at lower temperate while utilizing a heated air system that enables users to brown, roast and grill foods in a shorter amount of time, which microwave ovens cannot do.
Essentially, there are five basic types of microwave ovens: over-the-range, convection, built-in, commercial and countertop microwaves. The type you need depends on your cooking space and cooking needs. Convection microwaves do differ from regular microwaves, as they are a combination between a standard microwave and a convection oven. This particular appliance enables food to be cooked quickly, yet come out browned or crisped, as in a convection oven.
There are two basic types of convection ovens: third-element convection ovens and European convection ovens. Both use a convection fan to force hot air around the food, but third-element convection ovens also have an additional heating element near the fan that allows it to blow preheated air.
Convection ovens should be considered to be nothing more than augmented traditional ovens that circulate heated air using a fan. Food warms faster in a convection oven than in a microwave or traditional oven because it features moving air, which strips away any cold air that would otherwise insulate the food. By quickly moving hot air around the food, convection ovens operate at a lower temperature than conventional ovens while still managing to cook food more quickly.
Microwaves aren't really "ovens" in the traditional sense; they're more like kitchen appliances that heat food. A microwave's radiation heats water and other polarized molecules within the food placed inside the appliance. Microwaves are capable of thoroughly heating foods without necessarily cooking them, which other appliances cannot do.
A microwave shouldn't be considered as an oven replacement; it heats food quickly and efficiently, but cannot brown or cook food the way a convection oven could. It also cannot reach the temperatures that ovens do. If you purchase a convection oven, keep in mind that it will have about a 50-degree reduction in cooking temperature, compared to a conventional oven.
The most obvious benefit of having a microwave is being able to quickly heat up leftovers or other cold food, but convection ovens aren't really on the same level. They operate differently and enable users to cook meat and similar food in half the time as traditional ovens, while also cooking at lower temperatures. A microwave cannot be replaced by a convection oven or vice versa; they each have their own distinct benefits.
Any form of cooking, whether by microwave or convection oven, will destroy many nutrients in the food being cooked. Microwaves in particular convert vitamin B12 from active to inactive form, which makes approximately 40 percent of the B12 contained in foods unusable.