Actually, the one with Ledesma is the normal di Sarli -- the Florio was a backup that made it onto a record by accident (the Florio is easy to spot since it's much shorter, less than 2 minutes, with a lot of the orchestra parts left on the cutting floor).
The Spotify one that is 4:02 is definitely Ledesma. The other one (also 'Archivo RCA') that is 1:53 is Florio.
Ages ago, I used Audacity to chop the intro out of one version, and bolt it on to the other. The sound doesn't quite match (I don't know how they could ever have released the Florio version 'complete') but it does make for an interesting comparison. I have played it in a Milonga, without anyone commenting. The irony is that the commercial release of the Florio was probably just a mastering error that has gone uncorrected. On my RCA Victor 100 Anos CD, the track is actually labelled as Ledesma @ 4:03, but that's not what we have.
No, I meant ending one tanda with one version of Fumando Espero, inserting a cortina, and starting the next tanda with Fumando Espero again --by the same singer but a different orchestra. Obviously that is 'against the rules' but in this case I'll gladly flaunt my defiance ;-).
I think I'd pick 'De Qué Podemos Hablar' and 'Novia Provinciana' to add to the Di Sarli tanda (and since we're not following rules anymore, after the last word of Novia Provinciana has said 'Adiós!' to Ledesma, I'd bolt on 'Noche de Locura' by another singer to drown my sorrows.)
That's my gut feeling. Should try to see how it pans out...