[inquisitor]

Just for clarification:

What used to be marketed as "Lidl Mobile" has been rebranded to "Fonic Mobile" (not to be mixed up with just "Fonic") since Lidl started partnering with Vodafone and selling their services under the "Lidl Connect" brand.
Although Lidl continues to sell vouchers for the old product (just buy Fonic vouchers) you have to be careful because vouchers for the new product "Lidl Connect" will not work for the old SIM cards and vice versa.

During the past 2-3 performance of the eplus network has improved substantially and they used to have an even better 3G coverage than O2. However as part of the acquisition of eplus by O2 both networks are in the process of technical merger. As a first step 3G roaming has been enabled between O2 and eplus so customers of both networks will automatically register on whichever network gives a stronger signal. As a result 3G coverage for O2 and former eplus customers has immediately expanded significantly.
So no matter if you opt for AldiTalk or your old Lidl Mobile SIM cards, you will have the same 3G coverage. However when it comes to 4G AldiTalk provides the advantage of some urban LTE1800 coverage while Lidl Mobile SIM cards remain excluded from any 4G service for the time being.