Think you'll find the pro 28 bit gives it away, ie 28 kw. ( only suitable for 1 bed flat, where did you here this rubbish?)
I heard it on Vaillant's own website. Have a look you're self...
Yes I see what you mean about the output etc, thats why i asked if you knew why it was better than the PLUS variant.
Also on the installers forums I was lookin into it as I too couldn't see why it wouldnt be suitable. The only think I could come up with was that the pump is only single speed and they use cheaper parts (hence the 1 year warranty instead of the 2/3 on there other boilers). It says they are more suitable
for new builds.