It is a huge difference from 2011. Both the 2017 13" MacBook Pro and the 12" MacBook are awesome. The touch bar is really cool. I like them both very much but the 12" really nails it. It's so small and light. I would love to see Apple move to ARM but what they have already accomplished with the MacBook is really good.
I like ARM, like the iPad, because you never really turn it off. I'd like to see that but with a Mac. Hoping we are getting there. ARM-based machines are going to be spectacular.
I think if Apple move to ARM on the Mac it will be with the MacBook first, it's so small and light that i think it could run ARM well and even be a kind of experiment for Apple to see how well people like it.
My worry with replacing my 2011 MacBook Pro with a MacBook is first the screen size (i have a 15" MacBook Pro and 27" iMac at home) but secondly i obviously want something that is much faster than my current 2011 MacBook Pro other wise i would just stick with what i've got (altho the battery life isn't as good anymore and it tend to heat up a lot with the fans going in the background). However i'm going to wait and see what Apple update this year (possibly at WWDC) and then make a decision otherwise i feel like i'll never update and just keep going round and round in circles.