Ah interesting, I researched and my understanding is that his young daughter was very ill and the demands of touring meant just too much time away from family. It was agreed six months in advance that he would go but the band asked him to keep it quiet. ‘Officially’ there was no rivalry with him and Collins despite definite artistic differences. At Genesis’s reunion a few years ago, Gabriel was there in the audience and hung out with them all afterwards. We perhaps will never entirely know if or what extent a rift was but I think it was all more amicable than the press likes to make out. I’m no expert though. As I said, not a huge fan of them in any era!

As a colossal Genesis-’70s era fan [and not one of Gabriel’s / Collins’ solo careers] I’ d say PC is a lighter, poplike alternative to the heavier, more soul – oriented Gabriel’s voice.
Given that, it’s easier for Gabriel to sound like Collins, as he certainly does here, but not the other way around.
Another guy who sounds quite close to Collins [including the “lightweight” element] is Cat Stevens / Yusuf Islam. Funny thing is, I can instantly imagine PC singing “Oh Very Young”, or “Morning Has Broken”, or Cat Stevens singing …the entire Phil Collins repertoire. But not Cat Stevens doing much of Gabriel’s stuff…
The officially given reason why PG left Genesis is that, having family issues [his wife’s difficult first pregnancy] he couldn’t follow the band’s exhausting schedule, something the other members weren’t willing to tolerate.
Interestingly, of all 4, it was basically Phil who pushed for ousting him!