When to use chicken thigh versus breast?
Well, as to the difference in taste, I suggest the best way to find out is to try both (cooked, of course). If you have access to Cooks Illustrated (as opposed to just watching the TV show on PBS), they have recipes for both roast chicken breast and roast thighs—make both, and the flavor differences should be readily apparent.

As far as cooking goes, chicken breast has very little fat and very little collagen. Typically, chicken breast is cooked to 165°F/74°C (USDA recommendation for food safety), which is actually a little on the overdone side taste-wise. So various tricks like brining are needed to keep it juicy.

Chicken thigh has more of both fat and collagen, which allows it to take a higher temperature without drying out. Cooking chicken thigh to 175°F/80°C is fairly common. It also is much more suited to slow cooking, which allows the collagen to convert to gelatin (which gives a moist feel to the meat and also a nice flavor).

In this particular case, checking two Cooks Illustrated recipes for orange-flavored chicken (one deep-fried, one baked) they both note boneless, skinless breast may be substituted, but they prefer the flavor of thigh.

So you can use either. Use whichever one you think tastes better.