Picco engines are good but when it comes to replacing the conrod they are quite expensive. I'd stick with Alpha, you get a lot for your money and they are very easy to tune. When it comes to replacing the conrod, they are around £15. The Go GXR range are very good too and even come with a spare conrod. It's recommended you change this after 2 gallon.
Don't get too hung up on run-times as they vary from driver to driver and is dependant on how heavy you are with the throttle and how comfortable you are with leaning an engine to within an inch of it's life!. Most .21 race engines will easily do 7.5-8mins, the Picco and Alpha are no exception.
