I have always stuck to Varta rather than BOSCH - probably because in the parts department at my local MB dealership they used to have a sales display showing cut-outs of 'inferior' non-MB parts verses the cut-outs of the 'superior' MB parts. The 'inferior' non-MB parts looked like they carry the livery from BOSCH although the manufacturer logos were carefully removed by strategically cutting the products in half to expose the innards.
I was surprised to learn via this thread that the batteries from BOSCH and VARTA are essentially the same product! However, you might want to read this discussion about BOSCH vs VARTA batteries on the Money Saving Expert website to make your own minds up about the wisdom of buying a BOSCH or VARTA battery for your car.
Bosch Batteries - The Truth from Bosch - MoneySavingExpert.com Forums
It seems that the source of his problem was that due to a mistake made by the retailer he had no proof-of-purchase for the Bosch battery (the retailer supplied a Bosch battery but mistakenly wrote 'Varta' on the invoice).
It would be interesting to see what sort of warranty replacement service Bosch would have offered him had he been able to produce an invoice showing the purchase date of his Bosch battery.
Although, even so, reverting to 12 months from day of manufacture in the absence of proof-of-purchase seems a bit harsh. The flip-side is, of course, that we don't know what service Varta would have offered if he told them he had a Varta battery but no proof-of-purchase?
And, what compounded matters further, was his inability to raise this with the retailer who sold him the battery in the first place, because it wasn't worth his while to travel back to the shop.
But it does not end here... if I understand correctly, he also complains about the length of the warranty, which is stated as 3 years plus 1 year, but the extra 1 year is excluded form the UK?
So in short clearly he did not have a very good experience, but to be fair to Bosch there's also a set of unique circumstances here. Plus it was 4 years ago - things may changed since.
In summary it was an interesting read, but I doubt it will influence my decision if I ever have to to choose between Varta and Bosch...