picking a training partner
You know ...
One should not look at the belt, or hakama, or even consider the rank/pecking order of a dojo when partnering.
It is plain bad manners to not to consider all your partners as compatriots/friends in aikido training.
If you live long enough, reach 10th dan, you will be allowed to wear a white belt again and complete the circle of change.
If you do not believe that mastering a martial discipline is becoming a beginner again ...
Maybe you should start.
In the end, whether we are student, teacher, or master, we are all human beings just trying to get along ....
Learn to enjoy practice, laugh at your proficiency or lack of proficiency, and it won't matter who you go with, it will always be fun.
Think about your partner in these terms and see if your answer leans towards going with everyone?