Both are excellent processors but based on what you tell us, and even though I always tend to lean towards AMD products, I am going to say take the i3 machine for your uses.
The i3 has superior single threaded performance, as you can see by the benchmarks:
http://www.anandtech.com/bench/Product/118?vs=85
Obviously, the Phenom II is better in a strictly multi-threaded environment but this does not sound like your scenario to me.
I currently have an Athlon IIx4 at 3.2GHz and I occasionally think my single threaded performance is lacking. But I am glad of my choice because I work with virtual managers and gaming. But I have found that even opening 20 tabs at the same time in chrome browser will only use one CPU core. Although this may change, the single threaded performance of the i3 will definitely provide you with benefit.
All that said, I personally believe that you will not notice a difference between the two processors in practicality.
I also agree with mosox, if that can be made an option. Very few people need more than 4GB of ram and the phenom II 955 or 965 would provide enough additional single threaded speed to make it a better choice. In fact, a single core of the 965 is faster than a single core of the i3. The 955 will be about on par:
http://www.anandtech.com/bench/Product/118?vs=102