My primary issue with Connect at the moment is it desperately needs a reduction in the amount of taps to do anything. It takes 3 to download an image, and 4 to subscribe to communities. Both of these are things I feel should be in the ellipsis menu of any post, but currently you have to click through to the post or community. Meanwhile there are a dozen things in there I rarely use absolut flooding the menu. I also wish it saved comment drafts, but that is relatively minor.
It just needs some reprioritizing of actions and it would be perfect IMO.
I've never personally used the machine you're referring to, but unless you're doing long video renders it likely won't matter. Programming takes very little resources, even when using a debugger, compared to the torture tests reviewers use. Any heavy load comes in bursts of compiling/interpreting which also don't hit the machine anywhere close to as hard. Music production might be a bit more strenuous, but still well within the area of not having issues.
I'd say stick with the 14" if that's what you prefer. It's not designed to render videos 24/7, but even if you did that it's still pretty damn fast even when throttling.