I think Alcaraz is a great personality and can see why he is such a favourite. Sinner is very different, he's quieter and more restrained, almost robotic at times. Stereotypical Tyrolean.
If Sinner wasn't Italian I wouldn't be as keen to support him in these coin flip games with Alcaraz. I think the Spanish have been spoiled enough over the past 20 years having Rafa Nadal to support. Alcaraz will win many more trophies, maybe more than Sinner, but it should be a good rivalry for the next 10+ years. It'd also be nice to see if Jack Draper can become something of an Andy Murray and nick a GS here and there, but he has serious work to do. There are a few potential genuine challengers in that 18-23 bracket, but the scary thing is that the current big two are still only at the high end of that age range.