What is the difference between just adding brandy to burning it with regard to taste?
Time and theatric impact (flambe is often done table side in a restaurant) are the big difference.
- very quick, almost instant reduction of alcohol
- texture/composition changes to dish are limited due to short process
- visually dramatic
- subtle changes in flavor
Adding alcohol, then further cooking:
- longer cooking time to reduce alcohol
- longer cooking will have a different effect on texture/composition
- there will be changes in flavor, but in a different way from flambe
With most recipes, it comes down to time. If a long simmer to remove alcohol is undesired, you flambe. Example: Bananas Foster, if you simmered that for a long time, you'll get a hot bitter banana mush. Flambe is the better choice.
Without seeing your entire recipe: if your peppers are cooked a long time, you could simply add the alcohol and let the cooking reduce it. But if the recipe is a quick saute or similar, if you don't flambe, you may not get the flavor change the author intended. And, you may end up serving alcohol.