It depends on your playstyle. If t’s quite aggressive Blitz is definitely better because of his shield that will keep him alive much longer. But in case your style is quite passive you’d better choose Montagne. He’s not as good at attacking but has a strong shield that will protect his entire front. He’s not strong but his protection saves him in many situations. Besides, Monty’s a good option if your team has a strategy so if your teammates are ready to attack there’s no need for you to choose Blitz.