What suitcase is best for train travel in Europe?

Traveling by train across Europe can be an exciting adventure, but it definitely makes you reconsider your luggage choices. I’m currently planning a photography trip through Italy and France, and I’m looking for the best suitcase for this type of travel. I need something that’s durable and easy to handle in crowded train stations.

Some friends have recommended soft-sided backpacks for their versatility, while others swear by hard-shell suitcases for their protection. Given the frequent stops and various transfers, what features should I prioritize? Should I focus on weight, size, or maybe the number of compartments?

Has anyone found a suitcase that perfectly balances these needs for train travel? What do you think is essential when packing for a European trip?