If I were to choose just one, which supplement of the two will give me more noticeable results? I understand that they are a bit different, and it is best to use both, but if the case were like this?
Creatine has over 500 human clinical studies backing its effectiveness and safety. A BCAA supplement really isn't needed if you are already eating a high protein diet.
Creatine is also extremely inexpensive. Most creatine supplements cost around 50 cents per serving.
I definitely second the above mentioned opinions - creatine all the way. It is completely safe to use, and it really makes a difference. What you get from BCAA's can be easily achieved from a balanced nutrition plan.
I would go with creatine because you get good results from it and because it is easier to get enough protein than to try to eat enough creatine containing foods each day.