That's a really tough call and there are too many factors that you did not list. What is your rank? How much experience do you have? You mentioned 10 years but I don't know what it is 10 years of and how consistent, etc.
What are your goals?
If you are a white or blue belt and your friends are all whites and blues then you should probably find a way to see the higher level instructor, because, after all, other white and blue belts can only take you so far.
If there's a good purple, brown or black belt among your friends then stick with them if you are happy there. Even if there is only a purple or two, there are some great instructional videos out there. Where there's a will, there's a way.
Could you get to the high level instructor once a week? You mentioned that you would be working with him alone, which tells me that you would only have one body to work with, which would also slow your game down.
Could you bring the high-level instructor down to your buddies' place once in a while instead of you going up to see him, or is there a conflict of interest there?
If you have to make a choice between the two, here's how I feel about it: if you can call these people your friends, and you say that they really have helped your game and that you feel good that you are a part of that group, then you cannot put a price on it. Money isn't even a factor in that instance. If it's a matter of once you walk out you risk damaging your relationship with them, I wouldn't even consider doing it.
Always remember that the devil you know is better than the devil you don't.
I would stick around where I was happy and comfortable.
See if you could find a way to get to the high level instructor once or twice a month if it doesn't strain any political ties.
Last, count your blessings that you have a great group of buddies right down the street from you. I have to drive 35 minutes for it but still count my blessings every day that I am there.