It depends on where you are touring and your comfort level.

In North America my wife and I have found that most motels and B&Bs have someplace safe to store our bikes. A lot of motels/hotels will let you take them into the rooms.

Europe is a little different. Hotels will generally have a storage area that is relatively secure. However, they will not usually let you bring bikes into the rooms.

My point is that almost any decent lock will work. We each carry a medium weight 6' cable and beefy locks. Both locks use the same keys, which is good backup in case one of the keys gets lost. We use this setup regardless of the type of tour we are doing. Almost all our tours are a combination of motels, hostels, camping etc.

A U-lock and a cable will give you a little more flexibility. We mainly try to protect against opportunistic thieves; professionals will have the tools to cut through almost any lock. It would take 2 U-locks to lock the bikes properly, given there is something suitable to lock them to.

Sometimes a little creativity is needed as in this case, a hotel parking garage in Spain.