Hi Jay, Udaipur, the City of Lakes is an absolute beauty after the rains. Lake Pichola is bubbling with water. Sajjangarh Palace, also known as Monsoon Palace, is surrounded by greenery. Even the surrounding hills are clad in green. A 3-day trip is ideal of Udaipur as it gives you two days to explore attractions in and around Udaipur and one day to visit Kumbhalgarh Fort and Ranakpur Jain Temple.
Rajasthan has a own charm in moonson season. every place depend upon your taste u can visit. but udaipur is the best . udaipur is the city of lake and also know as "Venice of the earth ". you can visit sajjan garh palace, taj lake palace and city palace too. you can feel refresh air which hive u refreshment in your life.
Udaipur will be better as per my view. For instance, you can imagine those little droplets falling in Fateh Sagar lake and you are enjoying those merges on the shore of lake, Exploring City Palace with clouds over and watching that puppet show and traditional dance at night with cool breeze flowing. Jaipur has sight seeing mainly with forts but Udaipur has lakes and activities in addition to forts to enjoy.
I have been to both Udaipur and Jaipur. I felt that Udaipur is more of a romantic place to go with your partner. With beautiful lakes and sunsets you will love the city. Udaipur also offers many attractions like City Palace, Jag Mandir, Bagore ki Haweli, Sajjangarh, Karni Mata Temple (small trek) with cable car ..etc. Jaipur is good for its Amer and Jalmahal fort and you can roam around the city in a day. Both the places have its own charm. You decide!