It sounds like portability and battery life top the OP’s list of priorities. For me, when I was looking to upgrade my 2010 MB Air a few weeks ago, it was battery life (mine was down to a couple of hours, and I sometimes work untethered) and eye-friendliness, as mine are aging and increasingly tired out by hours and hours staring at a screen all day. For that reason, after playing with a Retina screen Mac at the Apple Store, another Air was right out. That left the two Retina options: the new MacBook (whose appearance I’d been awaiting before deciding) and the MB Pro.
After checking it out at the Apple store, I leaned initially toward the new MB because I have to tote it to campus thrice a week, but two factors weighed against it. First, Apple informed me that the MB would NOT support my 2008 24" Apple Cinema Display. I use that for most of my Scrivening because I need to be able to display the binder, two docs, and often the info panel all at once, and that gets pretty cramped on a laptop screen. Since the ACD’s max resolution is higher than my old Air’s, but lower than Retina, either Retina MacBook would ease my eyestrain when it’s plugged into the ACD. And it’s likely that Monoprice or Amazon will someday make an adapter that would allow the MB to work with my display. But that option doesn’t exist now, and for various reasons, I can’t wait any longer to upgrade. The MBP, by contrast, allows me to plug the ACD directly into it with no adapter needed, saving me up to $50 even assuming an adapter is someday available.
The other factor was cost. Right when I was making up my mind, Best Buy offered $200 off the brand new 2015 MBPs for a couple days. (They also discounted the Airs by a similar amount, but I expect no such discounts on the MB for a year or so because it’s new and sexy and doesn’t need to be discounted to sell out.) BB also let me subtract my academic discount from the sale price. So that meant I’d be paying at least $200 and probably more like $250 more (counting as-yet-nonexistent adapter) for a MB over a MBP. A pound and a half of weight wasn’t worth that much money. And of course, there’s still no guarantee that I will ever be able to use the current MB with my seven year old display, which I did not want to give up.
So I grabbed the MBP for $1049, which I consider a terrific bargain. So far, the added weight hasn’t disturbed me; I can’t tell the difference between the MBP and my old Air. when I carry it, and it’s actually smidgen smaller in footprint. I’ve never yet used the MBP long enough for the battery to expire, but I’m regularly getting six hours of writing/browsing/email on it, with not even half the battery life gone. The ForceTouch trackpad is fine but not all that useful yet, and the keyboard is great, not that I noticed much difference on the MB’s new shallow keyboard in a few minutes of typing at the store. But some writers have complained mightily about it so you might want to field test typing on it as much as possible.
What made the biggest difference, especially in Scrivener and iAWriter, is that retina screen, and that’s what I’d urge you to consider, although your eyes are probably younger than mine. Working with text is even better on the Retina MacBook Pro screen itself, which is higher res than my my monitor.
The new MB is a thing of beauty and I fully expect to have one, or rather its successor, in a few years. If it had worked with my display, I might have gone for one. But for now, I’m just amazed at how much value, portability and eye ease the 13" Retina MB Pro offers. It’s a great Scrivening machine.