Hi,
I'd like to say, if it makes sense to have link there, I would use that link. Thats allway the first thing I think about when I link externally. In that case, I am not thinking "I need that link" so I would. In that case I dont have problems to chose rel="nofollow".
Special in sitewide footer links I would use nofollow and you should (excepted alternate language sites or something like that). It was John Muller who told Web Design Agencys wich are linking sitewide in footer (with brand name) that they should think about using nofollow (round about april this 2015). Guess thats not really the same thing here, if its the same company.
For the 3 cases - what makes the most sense? Does a link in the footer on the hompage makes sense? Is it better for any human being to have these links sitewide? Makes it more sense to have a single page?
I have different clients with all 3 types, all without penalty (in sitewide links cases, the links are rel="nofollow" and the sites are the same company). I think you can use follow, but why take a risk.
I often cite Cyrus Shepard in that sitewide-footer case and I agree 100% with him, so I cite again: "Don't link externally in the footer. Just don't. I'm not going to go into the reasons. Just don't do that."
https://mza.bundledseo.com/blog/the-rules-of-link-building-whiteboard-friday