Building on someone's (forgot who said it, sorry) previous point:
The ASDA CEO appointed in January came over from Sainsbury's too. They seem to swap top management fairly regularly between the two and have been for the last few years.
Both stores brought in new contracts recently that pay more but otherwise are less favourable for the majority of colleagues. Sainsbury's made theirs compulsory, ASDA made them 'voluntary' although there was a lot of pressure on people to sign and it's generally accepted that it will become compulsory (I now presume this will happen around the merger date).
I worked for ASDA for 10 years and left last month. When I started there was so much focus on training staff to give great service and that has continuously been eroded. In theory they still spout the training angle but, in practise, they've struggled with the sudden steep increase in NMW and are hiring much less frequently and cutting available hours and so there's never enough colleagues to provide the service that customers should get.
I think that was a massive mistake as, since their USP used to be the fact they were cheaper and Aldi and Lidl have overtaken that, service was all they could have built on. Sainsbury's seem to have done similar but I'm only basing that on shopping in my local store in fairness.
I personally think they'll only keep the separate brands for a short time and then I think ASDA will go. They've been struggling for ages. I also think at the very least they'll close all the ASDA Living stores as the majority of them aren't profitable, don't hit their targets and a lot of the products they sell are things people are happy to buy online.