The problem is not the file size, but when diff'ing text files which are made of a huge single line, so GitUp spends a lot of time computing the wrapping. And in Side-by-Side mode vs Unified mode, it needs to do it twice by definition, so it would be twice as slow.

In the meantime, I would recommend trying to mark such minified files as binary through the use of Git attributes. This way they won't even be diff'ed.