Does Trenitalia offer the welcome drink and snack on Saturday Frecciarossa trains? At https://www.trenitalia.com/tcom-en/Services/Welcome-drink it says it is offered every day of the week but at https://www.trenitalia.com/tcom-en/Frecce/Frecciarossa-1000 under the Business and Premium tabs it says it is offered Sunday to Friday.
Not certain, but the Italian version of the same welcome drink explanation doesn't mention it only being available Sunday through Friday. Keep in mind that the welcome drink and snack are similar to what you'd get in coach on a short-haul flight, plus the option of an inexpensive prosecco. It won't be a prepared-to-order cappuccino and a freshly baked brioche, although those might be available for purchase in the restaurant car.
Edit: To add an additional thought, I occasionally buy a Business/Premium/First Class ticket when a great Economy or Super Economy price is offered. If the difference in price from Standard is small, I think it's worth it for the additional comfort. But imo it wouldn't be worth the additional cost if the only consideration was the modest welcome drink and snack (usually also an Italian language newspaper).
I don't have an answer either but it's certainly not something I'd base a decision on. Your trip, your budget and your preference, certainly, but we've found 2nd class plenty comfortable enough, and just bring our own snacks/drinks along.
Depending on where you're headed, If traveling with more perks is desired then you might also take a look at Italotreno's Prima or Club Exec ticket "styles".
I booked premium super economy for Naples to Venice in May with the help of people on the forum. I wanted a little more comfort. Would have preferred Business Super Economy but it wasn’t worth the extra €65 for 2 of us. Plus I thought my SIL would enjoy talking to passengers while I like my quiet time.
Don’t know about the welcome drinks. It was not important to my decision. According to their website, Italitreno does not have a restaurant/snack car but you can order snacks ahead of departure. Trenitalia has both on high speed trains.
I cannot tell you for certain about Saturdays, but I can tell you that in dozens of trips on Frecciarossa and FR-1000 in Business Class while we lived there, we always got a snack. Always. Not much, but we were happy to have a coffee and a little bite.