I did this tour twice, and if you are short on time and have to make a choice on ruins, I think these are the best. These ruins are world-reknowned.
It is a 2.5-hour drive or so that takes you through more remote villages/towns of the Yucatan area. You are closer to Merida and that area, practically.
You will need comfortable shoes and light clothing, as it is warmer there than Cancun, and you will do a lot of walking.
We had a guided tour, and we were briefed on the history of the area and the invasion of the Spanish Conquistadors. Then you have some free time to walk around the pyramids or even climb them, as we did.
Truly a must-see; take lots of photos, and take water. There are a few cafes, and some tours stop for lunch, although the place where we stopped was marginal.