If you're still wondering...
We shop in all of them. Different shops for different things.
I wouldn't buy meat form Aldi or Lidl, we really don't like it. However, the deli selections, some of the fruit and veg (always closest to each now status), some of the tinned basics, tomatoes, beans etc are brilliant. Decent chocolate too.
Cleaning products of all sorts and that Random Aisle of Crap can sometimes throw up something decent.
Christmas always starts with crisps, nuts, panettone, etc, the variations are great.
But we've never been able to do a whole shop in either. They don't hold some of the things we think of as essential.
My best advice would be to go on looking for specific items to test. See which you so and don't like.