My toaster oven has a temperature gauge just like my oven 200-450 degrees. I opened a package of fish sticks and the instructions said "Do not cook in microwave or toaster oven." It only had instructions for cooking them in a regular oven. Do you have any idea why a toaster oven that can be put at the same temperature would not be good to use? 
Possible reasons:  Horrible temperature control This is simply a problem of cheap construction. One could theoretically build an excellent toaster oven with precise temperature control, but why would you? Low thermal mass If you get an oven to 400 oF and open it for long enough to put in food, the result is an oven at very slightly less than 400 oF, and which will quickly return to 400 oF.  Do that with a toaster oven, and who knows what temperature you'll get, or how quickly it will get to your desired temperature (if ever, see #1). This is not a slam at toaster ovens, this is just due to them being approximately 2% of the volume of a standard oven. Closeness to elements It's easy for toaster ovens interiors to vary by nearly 50 oF from middle to edge, simply based on distance to elements.  Now don't get me wrong, I once made some kicking Oysters Rockefeller in a toaster oven, when I thought that they would be the difference between serving an appetizer and being allowed to serve breakfast the next morning.  If you know what you're doing, and watch carefully and continually, a toaster oven can be an excellent source of high(ish) direct heat, but they are extremely difficult to control, and extremely unforgiving of errors.  I can't think of a circumstance where a toaster oven would be my first choice of cooking tool (and that includes microwave, campfire, plumber's blowtorch). 