When I started, I made the mistake of getting an overly wide and overly padded "comfort" saddle and it caused me more problems than it solved. I now ride on a well designed road saddle with minimal padding and a much narrower design. The important part, at least for me, was to find a saddle that hit my sit bones just right while keeping the pressure off other regions. It makes sense that a bigger butt needs a bigger seat, but really, your sit bones (the bottom of your pelvis) doesn't get any wider when you get heavier, and that is where you want to bear the weight.
Seat height and position are also important, as is overall bike fit. Depending on the frame geometry and the desired riding style, you want to divide your weight bearing between your feet, your butt and your arms. If you ride a bike like you sit on a bar stool, all of the weight is on your backside which isn't going to help pressure problems.
Padded shorts are great, invest in good ones, but don't expect a magic fix-all.
Of course, losing weight and building muscle in your thighs and backside will help a lot.