The crv is the subjectively ‘better’ vehicle and also would not want to buy a car that I had to replace the heater controls etc under the dash. Hard to say what is wrong with the heat. If you need more space the crv is also better choice. Offer them 4000-4500 and go for the Honda. It also likely has a timing chain so better long term maintenance costs. I believe the matrix has a belt

Supposedly the local mechanic inspected w a boroscope and the conrods/etc are still intact?