The sort of anecdotal evidence that I can put forward
is that the VAXes I
currently look after are more reliable than the 11/780s I looked after ten
or so years ago which in turn were significantly more reliable that the
DECsystem-10 I used to use. However, this is just my experience so it's
hardly hard scientific proof.
For hard evidence of that look at the maintence contract costs for a
minimum system 10, 780 and uVAX. IT's all there in black and white
(and dollars/pounds/Marks). Thre is no question that is true.