Both places have its own attractions: 1) You can expect rain in both places during first week of Jul. 2) Waterfalls are near Coorg and lake in Ooty ( 3) You can visit WLS on the way to Ooty (Muthumalai) and WLF from Coorg will again you need to travel. 4) Wayanad has all three attractions, which you can consider (100 Km from Mysore).
Udhagamandalam on the Nilgiri terrain is full of peaks, landscapes and natural lakes, which is the official home of Toda tribe. Kodagu in Karnataka is full of lush greenery, sprawling coffee plantations and awesome weather that is the home of Kodagu tribe. Both are lovely summer hill stations, though I would suggest Coorg is a must to visit.
Both have different places to visit, if you are planning a trip from Bangalore to coorg or Ooty, you can go from Mysore which is on the way and can visit few places in Mysore as well. if you are going to Ooty, the road trip will be just awesome. you will be able to see lots of birds and wild animals on the was near to bandipur national reverse and madumalai forest(the road way will go inside the forest)