The OreUI screens (in particular the new Play screen) are a major performance downgrade compared to the previous JSON UI screens. In extreme cases, the screens are unusable.

oreui_play_screen_performance.mp4

The above video is from Eckosoldier on Twitter.

There are also multiple noticeable lag spikes while a new OreUI screen is loading. JSON UI had only a single spike before the framerate quickly leveled out. Java Edition has no lag spikes at all, besides when switching resource packs.

oreui_screen_loading_lag_spikes.mp4

The above video was captured by me on a system with a Ryzen 5600x CPU, a NVIDIA 3080 GPU, and a full install on an NVME SSD. Other games such as Helldivers 2 on this same device have fully animated menus with more options and no lag spikes whatsoever.

Expected Result

OreUI performs the same or better than JSON UI.

Observed Result

OreUI performs significantly worse than JSON UI, with noticeable input lag, lag spikes, and jaggy scrolling.