I see you haven't gotten a reply...so I will add my feeble two cents worth here. I have seen and read much about MErida,but have never really entered the town. There appears to be a lot of cultural spots to visit and I hear the downtown is lovely.

Ciudad Campeche I have travelled through...only on the oceanside road. We did not stop. So that too,is feeble info. It had a modern flare to it. There were more modern constructions along that stretch of road and seemed less colonial than other towns I have visited.

Depends on what you are looking for and where you have previously visited. If I had to choose, I would go to Merida and visit museums and check out the open market. But that's just me.

I would also do a day trip to Dzibilchaltun to see the archeological site there. It's on my list of places to visit.

I have spent many weeks in Yucatan. If you want cheap lodging in Merida I stay at Suites del Sol aprtments that can be rented daily or monthly, nice location, walking distance to everything. Otherwise there are numerous other hotels, but look for one in centro. Try YucatanToday.com As for Campeche, the centro area is colonial, especially inside the old city wall. Try frances drake hotel.