To see scenery, I think Chengdu is better, especially for food if you prefer spicy food. that will be much better. THe point is Jan seems not to be avery good month, or you can see Jiuzhaogou and Huanglong. You can travel Chengdu by your own. A tour guide is not a must. Well, you can see the panda in the breeding center. Anyway you need a plan to visit places in Chengdu and no problem to visit by public transportation, although have a car is convenient but costs a lot. The average temperature is about 5-6C in Chengdu, no more than 10C if the weather is sunny. Keep warm.