This is definitely an area for debate. I've seen the physical resolution of a 70/15 film frame estimated at 70MP, which is obviously a lot more than the ~8MP of 4k. The MP comparisons between film and digital are a little iffy though, and digital ought to be sharper within the limitations of that resolution than film. Ultimately it comes down to marketing but, having not had a direct comparison, I would still expect 70mm to look better than a digital projection system.
I think that digital LED domes might beat film because of the excellent light output and color reproduction, but I guess I'll have to shell out for the Sphere to find out as there are very few of that size.
I did some scanning for Universal. Depending on how the image is framed, you can usually just squeeze 4K from 35mm. The 70mm I had I easily pulled 8K from and I'm pretty sure I could have gone to 10K.
I think that digital LED domes might beat film because of the excellent light output and color reproduction, but I guess I'll have to shell out for the Sphere to find out as there are very few of that size.