I've honestly listened to Yoncheva and I think Elizabetta is too heavy for her. Though I often read opinions that this part is more lyric than it's usually performed.
So, I've calmly and with pleasure voted for Stoyanova. I heard her once, in 2017 or 2018, I knew her in recordings and broadcasts to the date. It was late enough in her career, but she sounded stable, as some younger singers don't. As for her voice size, it didn't seem small. She was well heard in the boxes (it was La Scala) and wasn't strained. The voice was beautiful in all registers. It was first time, when I realized that this opera is not only about charismatic villains Felipe and Éboli, dissolved by Cinderella-like Carlos. (My other lovely Elisabetta Tatiana Serjan began singing it lately). Of course, it was also a beautiful winter in Italy, but opera was one of wonderful parts of the journey.