As much as I like the appeal of the technology coming from the country highly dependant on gas (Germany), and therefore knowing a good boiler, I can't see how it's better at this stage
Respectfully how would you know?
The Viessmann has...
Far better modulation 10:1 rather than 4:1 ish.
Stainless steel hex rather than aluminium
Extendible warranty to 12 yr
Bolt on weather comp
About the same price