I've been building a desktop app on GPUI on Windows, so a data point on start-up: most of our time to the first frame wasn't GPUI's layout or text at all, it was creating the Direct3D 11 device, about 150 ms, which is the graphics driver loading. Moving the device creation onto its own thread at the very start of the Windows platform setup, so it runs while everything else gets ready, took us from 278 ms to 222 ms. Memory at idle is similar: most of it is the driver, not the UI. So on Windows I'd compare these frameworks with the GPU setup measured separately, otherwise the driver dominates the numbers.