Agree with seant46. ULTIMATELY, it will depend on preference. If you have not already, you can try googling board size calculators, do a Youtube search on Board size/length etc and draw your own conclusions after ploughing through the advice. Riding a board smaller than the manufacturer's intended weight range for that board (i.e. you are heavier than the max weight rating for that board) may void some warranties so you may wish to keep that in mind. But even if you size down, it is unlikely you will break/snap the board easily. At 5'7, 148 is doable if its a "park board" and you want "flexy". (But in truth even Park boards have different purposes, i.e. big booter boards vs noodle jib boards so I guess the real answer is not only preference but depends what you want to do).