Train from Milan to Padua

They are both in the same train, 1st class will most likely be more space per seat (so less people in a car), and since the price is higher, less people opt for it, so also less people in that sense.....it is up to you if you want to save money in this case. If you buy tickets far enough in advance, they might be very close in price! I think I got a moist towelette and a snack and a beverage on the last 1st class train I took (like airplane service), but that was because I was traveling on a Saturday and the prices for 1st class were at the time 2 for 1 versus normal price in 2nd. But also it would depend on which type of train you chose (I just looked it up and it was options from regionales to high speed trains).

The high-speed trains only take two hours to do that route, and I hear that the really isn’t much difference in the physical experience between first and second class, so I would think second class would be fine.

Personally? Not worth the money, but I am cheap.

Would not matter to me
I’d go with the cheapest

The trains are perfectly comfortable for a 2 hour trip