It's optimization for a single process vs multiple processes. Additionally, when you free up your architecture and loose up the internal bindings between diffe

It's optimization for a single process vs multiple processes. Additionally, when you free up your architecture and loose up the internal bindings between different areas, you sometimes can open chances for significant improvments which prior where not possible, thus still be faster with a "worse" solution. Considering how old GNU Emacs is, how much historical problems it has and how often you hear that this and that can't be optimized for this and that reason, this seems like such a situation where loosing up would open faster roads long term.