Is your old teacher leaving the area? If not is he planning on opening an independent dojo, or willing to teach you privately? Or are there other schools in the area that you might find appealing?
Please don't take this the wrong way, but from the sound of things you've already answered your own question - you should leave. I think maybe at some level you would like to have other people tell you that it's okay to leave, which is understandable. If you are not happy and if you are being hampered in your training and development by your feelings about the new teacher, then by all means it is not only appropriate to leave, it is what you should do.
However, make sure that you do so with grace and decorum. Just a simple "I've been thinking about taking a break for a while and now just seems like a good time to do it" should suffice. Don't go into details, don't make a scene, and don't encourage anyone else to go with you. That way you don't lose face before your old sensei or your new one, and you also leave the door open to return should you choose to do so. If you are able to arrange a private tutelage with your old sensei, don't advertise it to your friends. If another friend leaves and you think he or she might wish to join your private session, then mention it to your sensei and let him decide whether to invite them.
I'm that seems like a right royal pain in the rear, and that from the sound of things you'd much rather let the new guy know exactly how you feel. I know how you feel - I've been there. Just remember, aikido is the Way of Harmony, and ask yourself how the cause of harmony and peace is served by what you say and do.
Good luck. It will not be easy, and you will have regrets. Be prepared to deal with that, keep your bridges intact instead of burning them, and you'll come through this just fine.