Both of these ingredients are reviewed on this website - go to the Dog Food Directory here
or alternatively select the food you are interested in and you will find that under the ingredients list there are items in green- they are hyperlinks so click on them and it will take you to a description of it.
Additionally, if you want to search for foods that don't contain beet, again go to the Dog Food Directory and look at the filters on the left hand side. Under Avoid Ingredients you can place a tick in sugar beet. There is no box for pea at the moment.
Some dogs may be intolerant of one or both of these. I would not refute what David has said about them but as they are used widely in dog food, there must be dogs who are living quite happy, healthy lives whilst being fed them. I personally know of a canine health professional who has fed her dogs for some years on a fish based product containing both of these ingredients except that the pea is flour rather than starch (don't know if there is a difference). The dogs are all very healthy and compete at a high level in sports such as agility and obedience.
As for your dilemma, you first need to look for a food with the named meat source at the head of the list, and in a decent amount percentage wise. After that you have to decide what sort of filler/carb source you prefer, the two groups being grains (rice, oats, maize etc) or, if you want grain free it will be potato or sweet potato. Trust your instinct and go by the condition of your dog - if he has a nice coat, is not overweight, is active, bright eyed, has nicely formed poo then the indications are that the food you have chosen is suitable for him.