From a PageRank perspective Google treats links to URLs in robots.txt the same way that it treats links with nofollow: it drops the PageRank that would usually go to that link. So in your case it doesn't matter what you do. Either way Google is going to drop the PageRank.
From a practical standpoint this doesn't matter. Having links that drop PageRank doesn't hurt the rankings of the linking pages. It doesn't matter if you have two nofollow links on those pages or 100, Google doesn't change how they rank. I've tested this. I've tried removing large lists of nofollowed links from pages to improving rankings. It just doesn't help.
My guess is that Google uses a domain authority signal much more prominently in its algorithm that it has ever disclosed. Bleeding PageRank ends up not mattering when domain authority is so important.
Using nofollow on internal links is a PageRank sculpting technique that was popular 10 years ago. It has fallen out of fashion because it doesn't appear to work anymore. At this point, I would recommend only using nofollow on external links that are ads or user generated content.