CC-BY or CC-NC?
If the topic is Open Access to refereed research journal articles, this is the wrong question to ask.
The right license, providing the right
re-use rights, will depend on the field of research, the specific research findings, and the researchers.*
But we are nowhere near ready to consider such questions yet, for the simple reason that
there is no basic Open Access yet.
We cannot remind ourselves often enough that Open Access is -- first and foremost -- about
access: What made Open Access possible was the advent of the online medium (the Internet and Web): It made it possible
to make refereed research journal articles accessible to all users, not just to those whose institutions could afford subscription access.
That possibility has been there for at least a quarter century now, and yet three quarters of research published yearly today is still accessible only to users whose institutions can afford subscription access.
So why are we talking about CC-BY vs. CC-NC, while still not having provided basic Open Access?
Institutions and funders should first and foremost
mandate making refereed research journal articles accessible to all users, not just those whose institutions can afford subscription access.
The ideal mandate would require the author's refereed final draft to be deposited in an OA repository immediately upon acceptance for publication, and also made OA immediately upon deposit.
A compromise that is much easier for everyone to adopt as a first step is to require the author's refereed final draft to be deposited in an OA repository immediately upon acceptance for publication, and strongly encourage (but not require) that it be made OA immediately upon deposit (and to put a cap on how long it is allowed to embargo OA).
Once immediate deposit has become universal, the first and biggest hurdle of OA -- still not surmounted after 25 years now -- will at last be surmounted.
And once that has at last happened, all the rest will follow:
-- the death of embargoes,
-- the growth of subscription cancellations, making subscriptions no longer sustainable to cover the costs of publishing,
-- the downsizing of publishing and its costs to just the peer review service alone
(all access-provision and archiving now being done via the worldwide network of OA repositories),
-- the conversion of journals to Gold OA at a fair, affordable, sustainable price, paid for out of a fraction of the subscription cancellation savings
(instead of double-paid, double-dipped and grotesquely over-priced, as now, when subscriptions cannot be cancelled because the Green OA version is not yet universal)
-- the licensing of as many re-use rights as users need and researchers want to provide.
Instead focusing prematurely and needlessly on CC-BY vs CC-NC today is putting the cart before the horse -- and getting us next to nowhere.
*In general, scientists prefer not to have their work altered without their permission. So the CC license that virtually all researchers would agree to is CC-ND: no derivatives (meaning the text cannot be altered). For allowing re-mix, it depends on the field and the researcher. And of course machine data-mineability for research as well as for search and retrieval are always desirable and beneficial.
But anothor contingency to bear in mind in this transitional period is this: What we need most is immediate, unembargoed OA. If we insist on a CC-BY license, publishers will insist on an OA embargo; I think many will insist even with CC-NC. The former would allow immediate free riding by rival publishers. The latter would still allow competing republication. So both encourage publishers to adopt embargoes.
In contrast, immediate-deposit Green works with or without publisher embargoes -- and once it becomes global, it will undermine all OA embargoes, thereby opening the door to subscription cancellations, Gold OA and as much CC as we want.
First things first. Mandate immediate-deposit. But don't turn it into a restriction on authors' journal choice by insisting on CC-X prematurely (and needlessly).
If it is not part of the mandate, of course, and a field has a preference for one of the CC licenses where posssible, its use can be recommended.