The meridian everytime. The Seneca is a **** can compared to a turbine pressurised meridian. I have significant hours in both including all the variants of each and the meridian is unsurpassed in performance. A fast high altitude cruiser that will get you over most weather.
It can handle the weather thrown at it with ease, but in reality they are so fast and can climb so high you don't even see it. I used to aim to fly everywhere at FL240/250 so rarely ever saw sig wx.
More than 80% of my hours are turbine and once you have flown them you dont want to go back to Pistons......