It's a matter of personal taste. I find the Prussian architecture that is present in Strasbourg and Metz not very appealing at all, and thus prefer the more classical french style found in Nancy.

Keep in mind there are numerous holidays in may for 2024 due to the relatively early Easter in the calendar year.

Labour Day, 08 Mai (Victory Day), Ascension (09 may), Pentecost Monday (20 may). In Alsace-Moselle there are stricter rules on Sunday and holiday openings, basically most everything not related to restauration and petrol stations will be closed. In the Meurthe-et-Moselle (thus Nancy), usually 08 mai and Pentecost Monday are nearly-normal days of operations.