I got to mess with both today, I bought a X-36 off a friend who just got the 45..
To me the 36 just felt.. more solid and sturdy than the 45... like more heavy duty... Its wierd.. I would probably still take the 45 over the 36 if the price was equal.. but I wouldent be a bit suprised if the average X36 holds up better and longer than the average X45..