Yes. HUGE difference. When I buy and cook fresh most butts take about 12 hours. When I cook frozen, I gotta wait 12 to 72 hours (depending on how I defrost) before I can start the 12 hour cook.
Other than that I don't notice much difference. I bought roughly 120lbs of butt last time it went on sale for .99lb here.
The tough part is planning far enough ahead to defrost in time. And then when it is defrosted or in the middle of the defrost, hope nothing comes up to pull you away.