Regional trains vs Frecce

Regional trains are not practical for travelling between larger cities when a direct Freccia connection exists. No reason not to travel on Freccia trains between both cities.

Also, check Italo Treno, the new private Italian rail operator (they use the same RFI tracks as Trenitalia, but much mode modern trains).

The "slower pace of travel" suddenly become annoying and bothersome. Nothing quaint about that. Depending on your itinerary a regional ticket will actually cost more than the lowest possible fare on high-speed trains, and you don't have assigned seat. So an awful choice all the way.

The Regional trains are more like a bus on rails. By the end of the day the cars will be more cluttered, less clean just from more people riding. Second class, where most people ride, will be more crowded. And the cars themselves are generally older than the newer cars on the high speeds. We have ridden a lot of Regional and WE think they are fine but the high speeds are more comfortable. My dividing line is around three, four hours. If train ride is going to be longer than that, I will opt for the high speed. For example - the difference is about hour - 2.5 hrs vs. 3.5 between Venice and Rome. For us, the extra hour is not that critical. You could compromise a little and go first class on the Regionals.

Grant it, you can get very cheap, discounted tickets on the high speed trains but lose all flexibility. We don't mind the trade off of speed for flexibility but that is our preference. May not work for you.

There are no direct regional trains between Venice and Florence. It would require some combination of regional trains to intermediate stops, which could get complicated. There are 2 direct Intercity trains each day, but those require reservations just like the high-speed trains. You might be able to purchase Intercity tickets that don’t have a reserved seat, but it probably means standing for at least part of the trip. The Intercity trains only run from Venice Mestre to Florence Rifredi, so you’ll need 2 additional regional tickets to complete the trip. Riding without a valid ticket on those short legs risks a hefty fine. Total cost: about €30 versus €45 base fare for the high-speed trains. I’ve pre-purchased discount tickets several times with no issues and would recommend going that route. If you’re not comfortable pre-purchasing on the Trenitalia website, buy your tickets in Italy a few days in advance when discount tickets might still be available. Or, just pay the €15 (about $20) per ticket difference for the convenience of not having to change trains a couple of times and getting there at least an hour faster.

Regional trains are trains that have the purpose of connecting commuters from small and midsize towns to the major city in the same region (hence the name regional).
Frecce (arrows) are high speed trains that connect major cities.
You should use either according to your intended destination.
If you need to travel from Florence (Tuscany's capital city) to Lucca or Pisa or Arezzo (all of which are Tuscan midsize cities about 1 hr from Florence), then the Regional trains are for you.
But if you want to travel from Rome to Florence or from Florence to Venice (major cities located about 300 km from each other), then the high speed trains are for you.
Intercity trains are middle of the road options. Not as fast or as posh as high speed trains, but definitely more comfortable and faster than Regionals.

You mention occasional stops along the way - regionale train travel must be completed within a certain time period (hours, not days) after you validate the ticket. The time window depends on the length of the trip, average is about 4-6 hours, so you might have time for a quick look around somewhere.

I traveled from Florence to Venice and back last week. I went to the Trenitalia window at train station and bought a ticket, and coming back I bought ticket from a machine, which took American credit cards (with a PIN #). Rode the fast train, it stopped in Bologna, Padua, Venice Mestre, and perhaps one more city I cannot remember. Very nice train. Cost was 45 Euros each way. I would not take the local train.

John, I take note of your phrase "occasional stops in towns along the way". Actually, the Regionale trains stop at every stop along the way. Nothing occasional about it. In general, Regionale trains take double the travel time over the Freccia trains but cost about 1/2 the fare. I don't see any Regionale trains that go directly to Florence from Venice. At best, you can go from Venezia Santa Lucia to Bologna, change trains and then go from Bologna to Firenze. The Freccia train is so much nicer and faster but if you fancy the Regionales, that's OK too.

You are stressing over nothing. You will be able to buy your tickets in the Frecce trains for spring travel,when they become available. Find out when Super Economy fares appear ( it has changed since I last bought them) and book right away when they do.. Make sure you register in the site and you will always be able to view your tickets. Print them out and bring them along. Then just board the correct train. It is much easier than you think.

Also check the new Italo trains as suggested. People have reported good experiences with the booking and travel.

As others have stated, buy the frecce tickets as soon as they become available on-line. I purchased in advance from home and bought tickets from Venice to Florence and from Florence to Rome for only 9 euros per leg. These are the super economy fares. The only downside is that you are tied into a specific train/date/time. If you know when you want to travel, there shouldn't be an issue buying in advance. Just make sure that you create an account and keep track of your tickets.

If your only concern about Frecce trains is using the website, you don't have to. You can buy tickets when you get to Italy, either from a machine (they take cash and US credit cards) or a ticket window. However, these will be full fare. If you can accept full fare prices (which, in Italy, aren't that high), don't even stress about getting tickets in advance. If you want the discounts, you do have to use the website in advance.

As said above, if you want to get advance discount tickets, look into Italo Treno, the newer competitor to Trenitalia. Reports on this Helpline say that their trains are very nice and that their website is easier to use than Trenitalia.