Lots of interesting comments and opinions- food for thought. Thank you all.
For giggles, I priced out flights and times on kayak for Air Dolomiti. The cheapest prices were mid afternoon, so we wouldn't get to our hotel significantly earlier than if we took the direct day train. And with 22 inch loaded suitcases, we'd have to pay a lot more for checked baggage, so it ends up not being any bargain.
And some of you are right about the night train not being about cost savings (vs a night in the hotel). Once you add in the extra cost for a couchette, you aren't saving much. It's all about the time savings, and having the extra hours on arrival. OTOH, those extra hours won't be much fun if you're dragging around from a poor night's sleep. Years ( and years, and YEARS) ago, we would night train to Paris or Rome when we lived in Munich, and it was pretty good. Heck, they're even gave you a boxed breakfast in the morning! But we were much younger then.
I showed this thread to DH and we discussed it. I think we'll opt for the direct day train just to make everything simpler. Thanks again for all of your comments.