Two completely different learning curves. If you want to learn to fly airplanes, buy an airplane. If you want to learn helicopters, buy a helicopter. You will not learn to fly a helicopter with an airplane. If you are looking for the basics of RC, get a car.

The well known fact is that airplanes are slightly easier than helicopters, and depending on size could be cheaper. Now that word worries me. Cheap and RC usually do not mix, unless you want headaches with poorly manufactured products.

After saying that and potentially (most likely) pissing some people off, I will say that it is your decision and literally it comes down to your budget and how much you want to spend in the hobby. Quite frankly, I feel that you need to do a lot more research because based on your question, you need to fine tune your goals.

Running the risk of getting a novel typed here why don't you write what you want (what prompted you to ask this question) so we can better understand the bottom line of your goals.

Rafael