Having said all this I would put money 10:1 on EASA
not getting their way. The 5-10k euros cost, plus the time wasted on the 7 exams, is just an insurance policy on the 1/10
why not? Fuel consumption, running costs?
Partly because where this would be done they have a lot of water, and if I am flying somebody else's plane, especially a Diamond, I want to be extra careful
For my own ownership purposes, a twin is not a useful proposition for me. Diamond will remain unproven for some 5 years and that is only if they accumulate a really excellent reliability record over that time.
The old piston twins don't interest me. Awesome running cost, and most of them attract the IFR charges. They are also very expensive to buy newish (they still make the Baron and the Seneca, I think) and the maintenance costs, especially the old ones, are eye watering. You are easily looking at fixed costs of £20k p.a. If I was upgrading from the TB20, a
Jetprop is the most logical choice.