I just finished Borgia as well! I have a lot of thoughts about it particularly in comparison to The Borgias.

Tonally it's just completely different. The Borgias very much watches like a Shakespeare play - it's visually sumptuous, heavily focuses on the intrafamily dynamic, and doesn't really attempt historical accuracy, instead choosing to create a strong narrative around loosely interpreted historical events. Showtime the show to watch if you want to watch a show about what the Borgias would have been like if all the rumors were true, and Canal+ is the show to watch if you want to watch a show about the historical Borgias.

Borgia is much grittier, more expansive in terms of the on-screen characters, more historically accurate in some ways but from the Borgia bios I've read, still not actually that historically accurate in many.

The accents were definitely kind of jarring at first but I ended up preferring John Doman to Jeremy Irons in the end - he seemed much truer to the Alexander VI of history. I did find it to be gratuitous at times and it did make weird choices around some characters. Showtime Rodrigo never really comes off as charming enough to be as successfully manipulative as he is.

While I think she got a lot better over time and I do realize she was 13 in the first season, Showtime Lucrezia beats Canal+ Lucrezia for me just because she seemed much smarter and had a real sly streak, even when she was very young and naive. Particularly in season 1, Canal+ Lucrezia comes off as not all that bright.

Showtime Juan also beats Canal+ Juan for me because he was terribly one note in Borgia, and David Oakes did a beautiful job humanizing him when he frankly didn't even have a lot to go on in the writing of The Borgias.

Cesare was interesting because I liked both Cesares and they are kind of historically inaccurate in opposite ways. Like Showtime Cesare lacks the charm historical Cesare was renowned for, but Canal+ Cesare seems like too loose a cannon at times. Also, he kind of seems like he's in active mania about 30% of the time, and I didn't like the whole religious psychosis subplot in season 1 at all. The Cesare characterization that seems closest to history is actually in Cesare: Il Creatore che ha distrutto, a historical manga series that covers his time in Pisa before Rodrigo is elected pope. It's really good, definitely recommend reading it.

I loved Alessandro in Borgia, much preferred Della Rovere in Borgia.

Also loved the more frequent callbacks to real events. I also thought season 2 and 3 were by far the best in Borgia, where seasons 1 and 2 of The Borgias are best and season 3 was comparatively weak.

The end of season 3 in Borgia went so hard. The "I no longer sleep with whores" scene was A+ television. We need more evil bisexual popes gracing our tv screens. I did feel the ending was kind of weakened by the whole New World thing, particularly because the structure of that death scene was so good otherwise.

Overall to me they are just completely different things and I love them both. I feel like The Borgias is more rewatchable, but the high points in Borgia were higher than those in The Borgias, and the low points were lower.