I need to buy an electronic keyboard which will mainly be used for recording and songwriting. I will not be performing live very much with it. I want to buy a used one. I have come across a used p-150 and a 400r. The 400r is much heavier and I understand it's a little older. I don't know how different the sounds are because they're in two different stores. The prices are relatively the same. Can anyone offer any advice as to which one I should buy?