A major reason guys make the choice to stay on the 767 is the training program and the culture on the 747 is so toxic. I want no part of it until they fix it (but they haven't asked my opinion on the matter!!). I will only make the choice to go back to the 747 for the difference in pay, not because I miss the plane so much. And in the more than four years I've been on the twin, lifestyle on the whale has deteriorated to a level that is unappealing to me.
I bid very senior on the 767 in CVG (in the top 10%), and I'd certainly give that up by moving to the 747.
Above not withstanding, 767's horrible bid lines, our lack of reserve call-out rules, the company's refusal to publish flying that we all know exists, will ultimately force me to make a decision sooner rather than later...but not yet, the culture and the great training experience on the twin (right now) trump all the rest.
Good luck.