I have no idea about the Hyatt, but found the Pen to be ideally located for sightseeing with a very impressive view and excellent service. In terms of location; We found it very special to stay by the river and to visit the main temples (all located by or very close to the river) and other sights going with long tail boat directly from the Pen. You pay a little extra if the long tail boats take you to and from the Pen, but it is really a wonderful way to experience Bangkok for a first time visitor. Also the normal boat ("bus") going up and down the river is easy to take from the Pen, i.e. you just take the shuttle from the Pen to the jetty at the other siden and enter from there.