I keep seeing these conceptual complaints about OpenCode but it's unreasonably effective, so it's difficult to justify any time spent in changing to something else.

It hardly matters that it's vibe coded and ugly if it works well... and it does (for me).

Saving a few CPU cycles and reducing RAM utilization on my local system isn't going to meaningfully improve anything in and of itself; the wall time is all bounded by the model or by the code it's invoking (i.e. compiling or running the test suite).