1) not familiar with specs of sony cams, but i do think that most offerings on the market today are pretty solid.. if you are talking about body alone. the improvement made is generally hand in hand for all brands. what you do need to take into account is the direction each brand is taking, the lens system and options each brand has, the crop factor, and the flaws that you can handle and those that you cannot.
2) what is more important? both are equally important. i have seen shots from d70s winning international competitions still. i think it depends on what shot you are talking about. if you are doing landscapes, then frankly almost every dslr which can meet your megapixel rating has had decent image quality since a long time ago, if you stay at low iso.. which you will for most landscape photography.
for sports of course it is another story since iso comes into play etc. a camera only works because it has a sensor (in the body) and a lens. my advice is to buy into a system where you have faith in, like the feel of, and everything else will fall into place. in the past perhaps one could say that certain brands had stronger offerings of lens system compared to others.. but today with the proliferation of anti´-shake technology in-body, along with the fact that there are third party options available for most, if not all brands.. then i guess it is not hard to see that you probably do not have to be concerned about all that jazz.
