At a bearing seminar, the engineer from the bearing supplier was asked what grease was best. His answer was just use a grease with the correct rating for the application, and alway by a box of that grease so you always use the same grease consistently. He said that not mixing greases is way more important than the grease brand.
This had a oil rep come out and show how using 2 different greases was what caused bearings to look like they were packed with dirt. We just laughed because after all these years we thought that it was dirt. Always clean out old grease if you're not sure you're using the same can.