The system is very efficient if you measure throughput. It does not feel as nice and you are pressured to pack very fast which is why the more upmarket stores use the Y-layout or at least a long surface after the cashier (never seen the closing bar in Germany though). Customers stopped caring as it is used for decades now. FWIW I usually pack while the items are scanned which means I can leave as soon as I paid which one can't do with the other layout.
But why card payment is so hideously slow in Germany is something I can't understand. After they gave you the final sum you need to tell the cashier that you want to pay with card, wait for the terminal to light up, insert the card (finally, up until recently you needed to hand the card to the cashier for them to insert it – technically you can insert earlier and it still works but many cashiers don't know and stop the process), wait once more, enter your PIN, wait once more, remove the card, wait again for the receipt to print (otherwise the cashier tells you stay as they can't verify payment before that). In the time it takes you can pay with the same card five times in Sweden – and didn't need to speak a word (great for me as my Swedish is only rudimental).
Card payment at Aldi (Süd) for me is about as fast as it takes Rewe to register that I put the card into the terminal. Aldi also never asks for signature and always goes for PIN because it's faster. It doesn't have to be slow, but sadly in most stores it is. (Debit card here, though. No idea how it is for credit cards and whether they work differently.)
If you ever have the chance to visit Sweden I urge you to try paying with card there (well, it's easier than cash there anyway). It's unbelievably fast.
But you are right, among the German stores Aldi has one of the best terminal.
But why card payment is so hideously slow in Germany is something I can't understand. After they gave you the final sum you need to tell the cashier that you want to pay with card, wait for the terminal to light up, insert the card (finally, up until recently you needed to hand the card to the cashier for them to insert it – technically you can insert earlier and it still works but many cashiers don't know and stop the process), wait once more, enter your PIN, wait once more, remove the card, wait again for the receipt to print (otherwise the cashier tells you stay as they can't verify payment before that). In the time it takes you can pay with the same card five times in Sweden – and didn't need to speak a word (great for me as my Swedish is only rudimental).