4K TV viewing - upscale to 4K or FHD?

Any comments re visual quality comparing 2 scenarios:

(1) Upscale source to 4K (assume TV will ‘pass through’ cleanly)

(2) Upscale source to FHD (assume TV will upscale for presentation)

Any generic comments re TV upscaling capabilities? I only have access to advertising statements which understandably are of dubious value.

Additionally, when upscaling DVD sources, significant storage reductions are available by retaining original pixel shape, any comments on which is best?

Many thanks…

Using the Proteus model with manual settings, I can usually get FHD results that are better than the DVD source, but not as good as a typical Blu-ray. I don’t bother with 4K.

Depends a lot on the source. For some sources FHD is more than enough, for others 4K can make them shine even more…