Personally I prefer Lidl as I feel they have more big branded products but I also feel they both have exceptional prices unlike the money grabbing other supermarkets

Aldi for me. I like the idea of NOT having branded items there. Their own brand products are of a very high quality and I'd rather buy that than pay a premium price for a branded item. I hope it stays that way.

Tesco or iceland

In this area I would say Aldi have a slight edge, the shops are tidier, the products and service are also slightly better.

Only a slight difference, but enough to notice.

We only have a Lidl close by so I can't really compare it with Aldi. However, our local Lidl is generally very good. It has a bakery section too which is great.

My only main complaint is lack of checkout staff. I do understand that keeping staff levels low is one of the contributors to the low prices of course.

I've shopped at both and I prefer Aldi. I find Lidl doesn't feel as customer-friendly, I've gone in toward the end of the day and it's as if you're inconveniencing them to have them serve you at the till. And half the lights were off with an hour still left until closing time. It felt a bit weird, like I wasn't supposed to be there.

I don't have a problem with the quality or price at each store, although Aldi seems to have a bigger selection. Lidl sometimes feels like Netto with their non-grocery items in the middle of the store though, a bit disorganized.

I don't think you've understood the question

Lidl are terrible.
We went once & chucked a few quids worth of food away.
Aldi are superior in every way.