There are a couple new larger supermarkets planned in Heidelberg btw. The two new blocks they're building on Kurfürstenanlage (where they're currently tearing down the old state court) will include a 3,000 m² Edeka, probably under their E-Center brand. And sometime next year they're gonna start on the Nahversorgungszentrum Rohrbach
, a 6,000 m² supermarket center centered around a 3,400 m² Rewe and a 1,200 m² Aldi with the rest of the space taken by a number of smaller shops. If you're living in the exurbs down south, Wiesloch is currently building a similar center of the same size centered around a Rewe supermarket and a Promarkt electronics shop. If you're in the Schwetzingen area due west the new Kaufland near the train station might qualify with 3,300 m² too.
I find the grocery carts at most of the supermarkets to be too small for more than a few days' worth of food and other items
In my opinion the shopping carts are good for a week for a family of three or four (only few people in the area shop for bigger families, so it's a demand thing). Provided you're not packing it full of diapers or stuff like that. Which also is the traditional average turnover cycle for most Germans - saturday morning buy for the next week, during the week mostly perishables.
(And yes, they *are* trashy. As much as I like to save money, I just can't bear them. They're grim!).
I pretty much only shop at Real when i have to. Job-related bulk buys or some special offers usually, couple times per year (last time it was for 90 liters of Volvic - shopping cart almost broke down). Mostly skip out on it because it's not really worth the gas unless i'm passing by one anyway.
The Real shops were built in the late 70s / early 80s, and regarding their design etc they've noticably stayed in that period - and in the case of Brühl and Vogelstang that's despite Real only buying them five years ago (in fact the current design is more dreary than the one Walmart had in there, and more dreary than the one Massa and Wertkauf had in there before Walmart...). New Reals - like the one in Sandhofen, or a couple of those in Ludwigshafen - are bearable, relatively modern even.
Kaufland is mostly a no frills affair along similar lines as Aldi or Lidl. People tend to interpret that as cheap for some reason, even though that's not the case for either of them (except Lidl); at least unlike Aldi or Netto Kaufland doesn't present its wares on pallets...