which oil should i be running?

I run valvoline synpower 10w30, altho i have been thinking about trying the amsoil signature series 10w-30 for quite some time now, Just dont know that the amsoil is that much better then the valvoline to compensate for the much higher cost. And i dont run extremely long drain intervals, i change my oil and filter every 6 months regardless of how many miles i have put on the engine, but normally its in the 5 to 7 thousand mile range in 6 months.