If he's never had any problems, and didn't have any issues when you first got him, then it could be something you have done in the bridleling process; Anything from accidently bumping his teeth, pinching a lip, or pulling an ear too hard when putting the head stall on, can quickly cause a horse to resent the bridle being put on. SO, now it's up to you to figure out where the problem lies. I don't believe that a horse "just decides" that he doesn't like something, and I definitely don't agree with just switching to something else, simply because you can't figure out how to change it.
The first thing you need to 'reteach' him is to lower his head for you. This will make bridleing so much easier if he knows how to lower his head, and keep it lowered. Take your right hand and put it on the top of his poll and put light pressure with two or three fingers. I have my left hand on the front of his face, to keep it turned slightly toward me. Now just wait for him to 'give' to the pressure. AS SOON as he drops his head even a centimeter, release your right hand's pressure, and pet or scratch him on the neck. Rinse, wash, repeat until all you need to do is put your hand on his poll without necessarily applying pressure and he drops his head almost in your lap. Remember it is in the release of pressure that he will remember what it is you want, so be quick about releasing when he gives you the right answer.
Now lets move to another exercise, to rule out his 'ears' being the root cause of his problem. Take a halter that you can unclip the throatlatch, and leave the crown peice adjusted to where the halter fits the horse properly when it is on him. Now you are going to just practice slipping this on and off his head, over and over, ask him to lower his head, and slide the halter on, like you would a bridle; you will find out immediately if it's his ears that are the problem, if he raises his head when you go to slip it over them. Don't rush to slide it on before he can get out of your reach, instead, give him the cue for lowering his head again. Wait a few moments, before attempting to take the halter off; again, if he raises his head, instead of trying to quickly remove the halter, just ask him to lower his head, and then procede again. Rinse, wash, repeat, until he keeps his head lowered, for the entire process.
Now for the bit. For the initial stages of bitting him up again, I would remove the throatlatch, and brow band, so all you have is the crown peice, and bit. Now use your lowering cue, and insert your left thumb (the hand that will, or should be holding the bit for the horse to accept from), into the side of his mouth, to ask him to open his mouth. You will have your right hand up on his neck, holding the bridle, to slide over his head. If he tries to pull away, again, just give him the lower your head cue, and try again. Make sure when he opens his mouth for you that you don't bang his teeth with the mouthpeice, and pull the bridle on smoothly, not in a jerky manner...since this can tug on his mouth, and tweek his ears. good luck