I highly recommend the 4-stroke. I have been running them since they first hit the market. I am pretty sure they are just as fast as my lazermag xpress 8″-
I have never had a problem with the composite shaft-ever.
It starts very easy, in extreme cold 10 and below, it needs to warm up for some time- but then it is good to go.
Not mixing gas/oil is great- I love the four stroke-