If you aren't going to be overclocking that you really can't go wrong either way. The E5200 and the X2 6000+ are very close in performance at the stock speeds with the two chips trading wins in most benchmarks. Currently they are also priced about the same. Both options will also afford you an upgrade path at least for the time being. I'd probably go the AMD route myself as you can usually get a nicer AMD motherboard than an Intel motherboard for the same money.
If you do ever plan to overclock then you definitely want to buy the E5200 however.