Sorry not replying exactly as per the requested format. Just laying down some thoughts.
Responsive Grids are the way to go. For mass market appeal, it has to be Bootstrap over Foundation. In terms of what each does, I don't believe there is any real difference.
If it was a personal decision however, I would would choose yahoo's pure.css myself (
http://purecss.io/).
It is light, very non opinionated and will easily fit into a project without trying to take it over as the 800 ton Bootstrap Gorilla will do. It also doesn't depend on JQuery or try to do everything. It just gives you what you need for a responsive page. You can then load JQuery, either v1.x for legacy browser support or v2.x to ride the new wave, and any of the gazillion plugins to do whatever else you want to do.
With specific regard to Bootstrap and Foundation, beyond the selection of which of the two to go with, there is one of which version to go for.
Bootstrap is currently at v3 but are working on v4 which is currently at Alpha 2 stage.
Go for the established v3 or develop Alphaware (ZC 1.6.0) with Alphaware? There are obvious risks but also obvious benefits, not least since this will mean, depending on release timeframes, v1.6.0 would be current when released. I would be tempted to plumb for BS4 given that it is running very well but then, I am not the one people will be running to for support lol.
BS3 uses JQuery 1.x while BS4 requires v2.x.
Foundation is currently at v6.2.
Go for the battle tested but now discarded F5.x or the new, and in reality, general equivalent of BS4 in terms of its real development stage, F6.x? F6.0 and F6.1 were Alphaware, or Betaware at best and F6.2 is Betaware as well or should have maybe been labelled a Release Candidate. They are moving forward and may be okay to ride with ZURB on this.
F5.x uses JQuery 1.x while F6.x requires v2.x.
After all that, I would still go for purecss myself. Nothing much has happened with it for a while but then it isn't trying to throw the kitchen sink. Practically however, and since pure may well be dead and since it is never a good idea to tie a project such as this to a dead dependency, (different issue from a person like me doing one off websites) it has to be considered that Bootstrap is very prevalent and as someone already pointed out, many of the premium stuff around already use this. I am not sure how much hacking they are having to do and it might be better to just go with the flow and facilitate these.
If going for Bootstrap, I would pick BS4 as the I would guess we would be looking at a release for v1.6.0 in 2016 Q4 or 2017 perhaps. If running a store on v1.5.4 for instance, I would be reluctant to upgrade to v1.5.5 if v1.6.0 is just round the corner.
Given that v1.5.5 seems to be a fairly major update despite the minor dot point change, then perhaps v1.6.0 could be even more in depth with suitable time taken and in reality, I would think you must already be considering branding it as v2.0. The change to using a grid framework alone is big enough to warrant this I would have thought. Whatever other stuff had been pencilled in for a v2.0 would probably fit into a v2.1.
Anyway, interesting times for the project and best of luck!