I switched from mountain bike SPD pedals to road style pedals around 3 years ago and noticed pretty much zero difference in power transfer or feel. I was using stiff Shimano XC7 shoes and went for the similar RC7 road shoes.
Unless your shoes and/or pedal are worn out, you're experiencing hot spots, or you simply want to upgrade, I wouldn't bother. You may benefit more from better/stiffer shoes.