If you're planning on buying new, I would hope any decent shop would allow you to try a few different bikes and you can judge for yourself. A lot depends on what you will be doing with the bike. For a shortish distances at moderate pace, I would say a sit up and beg with a sprung saddle is probably most comfortable. Longer distances would be better with a road or touring bike, you don't want a long a very long reach to the bars, or bars that are too low as it will lead to discomfort after a few miles, I would err on the side of shorter as a longer stem is a possible fix if you feel too cramped.