The extension catalog[0] for Pi is really nice and I feel like Pi's TUI is a bit lighter than OpenCode's. I use my custom terminal multiplexer on my phone using Tailscale so the lighter TUI is much better on mobile.
I haven't used OpenCode in months so this might've changed. I'm also thinking of giving JCode a spin since it's even lighter but doesn't have extensions.
Pi to me felt like when you install a fresh OS with nothing on it and then customize it to your liking.
Sure there are some features that you'll want immediately but when I took at look at the number of slash commands that ship with Claude code I find it ridiculous.
Pi is more minimal and it can be used to create fancier custom agents for various tasks with plugins. OpenCode is nice if you are only coding though, then the difference isn't really that big unless you want an unusual interface/behavior.
I haven't used OpenCode in months so this might've changed. I'm also thinking of giving JCode a spin since it's even lighter but doesn't have extensions.
0. https://pi.dev/packages
1. https://github.com/1jehuang/jcode