Slightly un biased view here. I have to fix the things when they go wrong.
Reliability through a normal day is about the same. Rarely get called out to either.
When it comes to nigtstops however.
The 146 has an interior that is showing its age especially in the customers eye. I don't often have to fix things on the 400 that fell off onto someone's head.
The 400 takes about half the time of a 146 to put to bed if there are no defects.
Only have to put oil in two engines as opposed to four. and the 400 apu seems to me much more reliable that the 146.
With respect to the comment of the 400 being around as long as the 146. There is no way on earth. But that does have its good sides as many faults are down to the age of the 146. this will not be a problem on the 400 as it wont get there. it is a disposable aircraft.
And lastly many normal tasks such as wheel and brake changes are much easier on the 400 down to the design. The 146 was built in the age old British way over complicated and therefore labour intensive.
So my view is going towards the 400. But having said that the 146 has taught me a lot and made me a lot of money in the past, but I would still rather have the best of both worlds and be home three hours earlier and working the CRJ.
Bring on something new.