There is a section called "seat near to...." on the train website where you are supposed to choose a coach and a seat but there is no diagram to look at. Is there a way to do this that I have not discovered? Also, I have a choice between two trains for the same trip, the ES(Eurostar) and the IC (Intercity)...is one better than the other?
It is not necessary to use the "seat near to" and coach options unless you're traveling with someone who has booked tickets separately and you want to travel in the same coach and/or near someone within the same coach. As for the two types of trains, the Eurostar is the nicer (and usually newer) of the two and usually the faster of the two, although often not by a tremendously significant amount of time, but it does depend on the journey as you might have noticed when you were comparing times of arrival and departure.
If its a long trip, you may want to splurge for first class on the Eurostar train. It was an excellent memory for us when we went from Milan to Venice. We even went to the dining car and had a snack and glass of wine. I had always wanted to do that on a train. Great big windows and flowers on the tables! There were "stewardesses" and we were given magazines etc. Very nice. Not sure if its always like this, but it only cost about 20 extra euros and was well worth it.
I just took 4 trains in Italy - 2 were EuroStar (ES) and 2 were EuroCity (EC). The EuroStar is the fastest train with few stops and the EC stops at more cities. I traveled first class each time and if you are just 1 or 2 people, it's ideal to book the single seats facing each other on those trains. Otherwise you are two by two facing eachother and having to step over someone if you have a window seat and want to get out. IC's and others are slower and stop at many more towns. Depending on where you are headed, you may have a mixture of train types.
ES have dining cars, and I think depending on how long the trip is on the EC, there may or may not be a dining car. When there isn't (my trip from Como to Zurich did not have a dining car), someone comes by with a cart with snacks and drinks for purchase.