If you've been shooting 35 previously, the Pentax will feel more natural at first. Both systems have good optics, at least in my experience, although IMHO the Hasselblad wide angles are superior (but cost a lot more!). I've come to appreciate the square negative for its cropping possibilities, and because you only have to hold the camera one way, whether for vertical or horizontal framing. One of the biggest Hassie advantages, though, is having interchangeable backs--you can reload very quickly, mix different kinds of film, and even change format from 6x6 to 6x4.5 if you want to.