I'm pretty certain that more code is more difficult to maintain, period. Before you modify anything, you have to find the relevant piece of code, understand it

I'm pretty certain that more code is more difficult to maintain, period. Before you modify anything, you have to find the relevant piece of code, understand it, and understand all the dependencies' interfaces (or even part of their implementation, if the abstractions leak). I can't recall specific experimental result, but it seems, well, obvious, that all the above will be more difficult if there is more code to examine. Now you could argue that you could shrink the size of the code that one have to examine before making a modification, by increasing total code size. I don't believe it. Increased modularity means more code re-use in the first place, and therefore a smaller program.