My personal preference is Jepps. I think they're laid out in a more more logical fashion, and thus easier to use. When I was flying GA, however, I used NOS charts since they're cheaper. If you're an AOPA member, you can download approach plates for free from the website. Do this for your instrument flights and throw a current NOS book in your bag for diversions, and you're set.
On another note, a buddy of mine works in the FAA's charting office and says they're in the process of converting their charts to something more along the lines of what Jepps look like.