Probably the most important characteristic of a bike is one you enjoy riding because fits well. For short rides of 1/2 hour or an hour, the discomfort of a poor fit is endurable. It happens that when people enjoy riding, those rides get longer and in that case a well fitting and comfortable bike become more important.
Beyond the issue of comfort, suitability of purpose becomes important. If this is your first bike, then, in my opinion versatility becomes important. I got lucky in my bike because the bike shop put me on a just the right bike for my purposes. I go on speedier club rides but I can put a rack on the back to mount a trunk bag or saddle bags for errands around town such as shopping, post office or library runs. Since the bike is so useful, I use it a lot.