Best solution tested so far for me: the Pound Technology HD-Link cable. Can’t get something nicer with the ossc.
I think the Pound cable for the Xbox is a decent solution, but it’s not perfect. It’s very simple to use, and it’s only $30; but it’s still a component-to-HDMI converter, any games that have frequent video mode changes (not many, but they exist) are going to be frustrating to play due to the HDMI blackouts, it doesn’t do any deinterlacing for 480i or 1080i, it’s a passive device without any configuration (which may be a pro for some), and it doesn’t support 5.1 surround. It would definitely be useful if your TV or AV setup can’t accommodate YPbPr component, or if you’re using the console on its own, like if you were to bring it to a friend’s house for some system link fun.
The OSSC is a different solution for a slew of other problems, but it does have a few benefits over the Pound cable, like being able to line-double 480p to get 960p, which, when scaled, can get you a far sharper image than starting from 480p, it can bob-deinterlace 480i and 1080i for televisions that don’t support those modes over HDMI, and it doesn’t preclude you from using TOSLINK to get 5.1 surround. (I am aware of TOSLINK shims that fit between the console and the AV cable that would probably work, but they’re very hard to find.)
I think the best solution with the best fidelity, would be an internal HDMI mod, not unlike the UltraHDMI or DCHDMI. Something like that would (ideally) be able to read the digital RGB and audio (so it would use stereo or 5.1 surround as configured in the dashboard) directly from the motherboard instead of digitizing and converting analogue YPbPr or audio. It could come with a built-in scaler that could, like the UltraHDMI, scale everything to a given resolution, which would avoid HDMI dropouts; and it could, like the DCHDMI, line-multiply 480i and 480p to 960p, optionally windowboxing to 1080p, which would give a pixel-perfect scale without sacrificing image quality or compatibility. Even better if it came with a proper (optional, of course) deinterlacer for 480i and 1080i content rather than simply bob-deinterlacing.