I prefer Lidl over Aldi as the range is generally better, however the wine is better in Aldi.
Worth noting that Lidl have a reputation for overworking their staff. Not sure if Aldi is quite similar in that regard.
Also there seem to be a lot more Lidl stores around than Aldi ones, at least down south anyway.
Dunno about over working, but Aldi pay very well I hear.
We often pop down to NT'as local one to browse the specials. However, we tend to do main shopping in
Morrisons, the more local one (although there's not much in it distance wise.). I've never noticed any difference in the clientele or atmosphere, beyond Aldi being a smaller building.
However, I don't know that we'd save much on groceries at Aldi, as I'm a buyer of own brands. The comparative price adverts are always matched against brand names. A tin of Aldi tomatoes is cheaper than Napolitana, but more expensive than Morrisons or Sainsburys basic own brand.