I think it would be good to stay overnight on the island if you can find accommodation there, that way you’ll get to wander around in the evening and early morning when it is not overrun by thousands of visitors from the tour coaches.

i wouldnt bother staying on the actual island, its cheaper and easier to stay in a nearby town and make a daytrip of it. i stayed in Villedieu, not exactly close, but a charming town. bout 30 minute drive i believe.

It would be cheaper to stay off of the island and make a day trip out of it. I went with a group of friends and we stayed about 5 hours on the island but we basically saw the monastery and walked around the island. Just make sure to stay late enough to see the monastery lit up at night.

A few years ago my wife & I stayed a night on the island and I am really glad that we chose to do so. The hotel was not very expensive (much less than $100 equivalent, if I recall correctly). I think it was this one: www.lemoutonblanc.com

When booking by email, they gave me a choice between two rooms, one of which was about $10 more and was described as “with a sea view, but there are some steps.” That sounded pretty neat, and I would not have expected the hotel to have an elevator anyway, so I went for that.

So, we get there and walk up the (only) street, and go into the lobby of the hotel. We tell the lady our name and she looks up our reservation, grabs a key and says “follow me.” Instead of heading upstairs, she goes out the front door and into the street and heads up the hill, up the stairs by the parish church, along an alleyway, by the graveyard, up some more stairs and twists and turns until we arrived at a tiny door in a tower (the Logis du Chapeau Blanc). Typical small European hotel room with cramped bathroom, but we don’t care about that. The room had a little patio with a tree (which can be seen in aerial view photos of Mont St Michel). We LOVED it!

We got to walk the walls and watch the sunset and keep exploring after dark. If I had the choice of a room 30 minutes away for 30 bucks less I would still choose to pay more to stay on the island. Mont Saint Michel might be one of my favorite places in the world anyway, but staying within the walls made it much more special.

I don’t know about relative prices between hotel rooms on the island versus off, but that would be easy to check out online.

If you are renting a car, put your overnight stuff in a small bag to carry up, because you park down on the causeway and have a 2-3 minute walk up to the hotel(s).

I think the actual island is good enough for a visit, but I highly suggest spending a day and a night or two (or more?) in St. Malo. I enjoyed St. Malo much more than Mont St. Michel. (Although Mont St. Michel is a must see!)