The Frecciarossas will do the journey twice a day in Less than 7 hours. For now it's cheaper than SNCF, This Serenità fare seems to be tailored to attract new customers in the Age of Covid. 35 Euro, one way, per person. Putting December 20 on trenitalia.com as day of travel.
Since they are using Milan's main station instead of Porta Garibaldi, it's also a better option when you must transfer from/to another train.