Clarinet or Tenor Sax?

want to start on either one. I have been playin the piano for four years now and want to do band in high school. I know all the notes on the clarinet (one octave, Bb clarinet) and I have heard that the tenor sax is also in the same key resulting in useing the same keys to produce the same notes. My only problem is that I don't know which one to start wtih. Should I start with the clarinet or the tenor sax? And how heavy is a tenor sax (be exact).