We will be traveling in May and are looking for a one day trip from Paris. We did Strasbourg and Colmar a few years ago and they are our most favorite places. We like exploring and history, but also like having some things to do. We are not really into art museums. As of right now, Troyes or Lille look like they might be good choices. Any advice would be greatly appreciated.
Reims is also a good day trip...cathedral, WWII surrender museum, champagne tasting houses right in town. We walked from place to place (in our seventies) without any problems. I can't speak to Troyes or Lille.
Lille is a much bigger place and more vibrant too compared to Troyes. But the latter is to my opinion much more lovely. If you like the half-timbered building style (however not exactly the same) like in Alsace, I would certainly go to Troyes. It has a maze of little allies giving it an unique intimate character. I have visited it once and certainly want do that again.
Joan of Arc attended once Mass in the cathedral of Troyes on the way to Reims, where the Dauphin was proclaimed king Charles VII of France. From a historical point of view Reims is interesting as most kings where crowned in the cathedral there. Inside there is a little chapel devoted to Joan of Arc. But for the rest the cathedral is nowadays a bit empty, to see more you have to go to the adjacent museum. Still have to visit it and not so sure how much there is to see. Reims is further not so attractive, besides the things Judy notes.
I've been to Troyes but not yet to Lille. I liked Troyes a great deal and really appreciated seeing essentially no other non-French tourists.
I was not entranced by Reims as a city, though I acknowledge that there are things to see there. To me, it's just not a particularly physically attractive city.
If you haven't been to Rouen, you might consider it as well; it's gorgeous. Rouen is about an 80-minute train ride from Paris.