Well, Arriva aren't well known for providing modern, reliable, and comfortable transport for their customers.
You just have to look at Chiltern's class 165 units to see this. I don't think they have ever had any refurb during Arriva's lifetime holding the franchise.
Honestly, totally unfair criticism. Its a bit of an irrelevant point given franchises have refurbs agreed/not specified at the bid stage but...
Northern:
Full fleet refurbishment
Introduction of 195/331
Introduction & refurb of 170s (compare to EMR)
ATW:
Extensive, comprehensive and very high quality fleet refurb - especially when you compare with some of the contemporary refurbs.
GC:
Arriva signed off on extensive 180 refurb
Chiltern:
Full fleet seems to get refurbished once every few weeks (...yes this is facetious, but I dont live in the area and my only exposure is these forums, where, seemingly every other thread is about the 168s or 165s getting a refurb/repaint, I've never known one brand to carry so many different iterations of a similar livery).
XC:
Full ongoing fleet refurb (yes its been a while but I refer back to the initial point that its down to the DfT, rendering this list quite pointless).
And just to bring this back on topic... I'm pretty sure this is all moot anyway as its already been announced they're shaking the 180/221 tree for units on this run...