There are advantages of either supermarket.
I really rate the quality of Aldi and Lidl, which is usually at least the same as the major brands, or supermarket own brand finest level. I've rarely had problems that others always mention about poor quality fruit and veg.
I agree that you can't get absolutely everything there, but that makes for a quicker shop than trailing round a massive Asda (ours is on two levels and you have to go downstairs for a lot of non food items like toiletries which takes ages especially if you have to take a trolley on the escalator) and the range has expanded massively over the last few years, so the 'can't gets' list is much shorter than it used to be.
But in Asda there is a bigger range, so there won't be many things you can't get, plus their own brand or Smart Price range could often be cheaper than Aldi or Lidl, but often the quality will be poorer. I don't think their meat is very good either. But they often have good offers on branded goods. We usually go there to stock up on Quorn products that we can't get in Aldi, likewise Branston beans and canned soup as while I think most of Aldi products are excellent, I don't really like their canned soups or beans, but it is many years since I have tried them.
But I don't understand why people always get hung up on 'should I shop in Asda instead' or 'should I switch to Aldi or Lidl. You don't have to go to the same supermarket every week you know.
You also don't have to shop exactly once a week or buy the same things every week. You could alternate, swap around as you feel like it, or get a big Asda delivery every so often and then treat Aldi or Lidl like a top up shop and when you need bread, milk or fruit and veg, get it in Aldi and anything else you need while you are there.