As much as both are cheap outlets, there is a difference. Aldi carries a majority of own brands. 90% of an Aldi store is its own brands. There own brands are advertised as if it was an actual brand, but are owned by Aldi themselves. Lidl however, sells non-own brands, imported brands and own brands. Lidl also focuses on more non-own brands than Aldi does which is at times more appealing to consumers who want cheap, branded goods. I can't really pick a favourite because for me, there are things that are better at aldi and some are better at lidl. It boils down to preferences.