I have 3000 hrs in Seneca Fives and loved them to bits
remember too that the service ceiling engine out is around 16500 feet so over big mountains I would choose the Seneca any day.
Taking them up to 18 to 20K and the climb rate remains strong all the way with a TAS of over 200 Kts once up there.
Seneca ANY DAY but then I am biased with that loyal friend
Pace