For your budget and usage, you are looking at getting a Netbook. I think they usually come with the Intel Atom series processors.
Between AMD and Intel processors, AMD doesn't make high end processors, so if you need something heavy duty, there's no AMD equivalent to an i5-2500k or higher. The main difference between Intel and AMD at the low end and mid range processors is that AMD has more cores while Intel has better performance per core. What this means is that heavily threaded applications, like video encoding, will favor AMD. For anything that doesn't require as many cores, Intel will function better.