a) don't think it makes much of a difference, it's choice, really. I'd go for the cheaper one, leaves you more cash to enjoy your flying later
b) you'll have to get a checkout on any new airplane anyway (otherwise the club/FBO won't let you fly it) and that should be enough. While Cessnas and Pipers
are different, they remain in the same class of spamcan....
c) No. Stick with one type and don't needlessly complicate your life. Now go on and learn to fly