An interesting question under the circumstances.
I've done both B&W and colour printing in the chemical darkroom for about 30 years, finally closing my last darkroom in about 1998.
The answer to your question depends on the film format, though I've had literally billboard-sized blowups from medium format for advertising clients.
Assuming a high quality neg or transparency in all cases, and a fine-art application, I was never happy with larger than an 11X14" print from 35mm, or a 20X24" print from 6X6cm film. After that it seems that you're just enlarging grain, not displaying any additional real information.
Film speeds? Everything from ASA 2 (High Contast Copy film developed to continious tone back in the 1960's) to ISO 3200.
Ps: If you've never done any extensive darkroom work yourself, be aware of the potential pitfalls preventing achieving optimum image quality. These include...
- paralellism (or its lack) of the enlarger's head and base
- enlarging lens quality and allignment
- film flatness with glassless carriers.
- Newton rings with glass carriers
- paper flatness
- criticality of enlarger focus
- negative buckling from bulb heat
- use of the enlarging lens' optimium aperture (which may be at odds with having enough light to make a large print)
- eveness of illumination of the enlarging head
- resolution characteristics of the enlarging paper (and related limitations)
- loss of contrast when large prints are made, including reciprocity effects with related long exposures.
And, oh yes, did I mention film buckling? Speaking of which, medium format suffers from film flatness problems – big time, especially on the first shot after the roll has sat in the camera for more than 24 hours with a reverse curl.
And sheet film, well, did you remember to tap the holder to ensure that the film isn't buckeled in the holder? Nothing can screw up large format faster than buckled film, which happens more often than most LF photographers care to admit.
Digital prints on the other hand. Humm. Let's see. No film flatness problems, no buckling, no secondary optical path during the enlarging process, no focusing issues when enlarging, no Newton rings, no paralellism issues, no paper flatness issues.
Oh yes. Add to that an almost total lack of grain (noise) at all reasonable ISOs, no processing variability, no reciprocity failure, etc, etc.
I could go on. But, it's late, and I think (hope) I've made my point.
The good old days of film with it's superior quality? Uhh... No thanks. No way. No how.
PPs. Yes, I do still have a Canon 1V, as well as a film back for my Hasselblad. I do even occasionally shoot film, when its attributes are appropriate for a particular project. But, I would never go back to optical / printing in the chemical darkroom. Never.
Why? Image quality above all. Plus greater convenience, perfect repeatability, faster turn-around and lower cost. And finally, not having to work in the dark for hours (days) at a time breathing toxic chemical fumes. Give me a glass of Merlot in front of the computer screen any day.