"избрать" is an old-fashioned word used mainly in a ceremonial sense. "выбрать" is just an everyday word used for everything. For example, you can choose a beer and say "я выбрал". If you say "я избрал", it will sound funny in this case. But if you choose a wife or a president or a way in life, you can say either "избрал" or "выбрал", and it will not sound funny. In fact, "избрал" is more fitting here because of a serious nature of an event. This actually works with other words. For example, "изгнать" - "выгнать", "излечить" - "вылечить".