Does size really matter?

Hi everyone, I’m new here. Thinking about a new antenna. Not transmitting yet but have access to an 8 element and possibly a tower. My question is this. Towers are nice but I’m not sure how much advantage it would be to go to all the trouble. Would an extra 40 feet over what I would have mounted on my roof really help. I’m not in a valley and to my ESE would require several hundred feet to clear the mountain tops. So would another 40 or 50 feet help?