related pr will gain authority in your niche, thus giving you serp = traffic PR in return gives you PR and PR doesnt give you traffic.
In some cases unrelated backlinks with High PR will help but that's not the case always. Of course related niches work better but its hard to get those links. Don't just look for high PR check also if how many outbound links that site has. Even if the site has a high PR but has too many outbound links it will not be that valuable. I suggest you go get both of them.
I would definitely choose the earlier ones as a website having a page rank value of two is more valued by Google.