Most of the Mephisto models hovering in the U.K. have JetCat P-300Pro turbines. Various run amounts, some in the 100’s of flights. I think you should just go with the one you feel comfortable with. When the other 300N turbines were struggling to actually produce 300N the JetCat was tested at over 300N and the turbine is still produced with minor updates as JetCat learn from the ‘abuse’ Mephisto type flying gives the turbine. Others are on their 2nd/3rd attempt at that size turbine.
You could also consider the new P-250Pro-S turbine if you don’t need the full 300N. Test coming soon in RCJi