I purchased the 300h. First I am an **** financial guy. When I started my research I was interested in the 350. Then seeing the difference in gas mileage, but more importantly the relatively small premium in price for the 300h we went with the hybrid. Then I just had to get comfortable with the reliability of the hybrid technology. Typically the premium spread in price for a hybrid model is much higher, making the payback period too long in my opinion.
For the gas numbers you cited in question 2, I probably would have purchased the 350. Engine size not an important factor for us.