There is a 5kw difference, which is not small margin when looking at a Hybrid setup or are now looking at a full ASHP system?
Which, if any of the 2 quotes did a satisfactory heat loss calculation or did they both pluck a number out of the sky?
The 2 quotes are relatively similar in that what one offers better in one thing, the other betters in another but overall I’d say your latest quote has a slight edge.
Grant is made in Japan by Chofu if your interested. Have they quoted you for the solar panels you wanted and what battery manufacturer were they using?