On 2020-09-30 14:41:17 +0000, Dave Plowman (News) said:

I'd caution against taking just the advice of an installer. They are
likely to want the most profit and ease of supply and installation. The
devil you know... They ain't going to be worried if it lasts 10 years
against 20 for a better make.

I don't think there's much doubt about Vaillant. But other brands have
upped their game so there isn't that much between them in reliability
at least.