exact same weight.
exact same fill type (down, synthetic, doesn’t matter). exact same shell material. exact same everything except design.
the vest concentrates its insulation to where it’s most needed, the core. as the vest uses less material and thus saves a bit of weight, it also has a bit more insulation too. however, it allows much heat to be “vented” through the arms.
which one do you think would “feel” warmer wearing?
assume you’re doing light chores around camp. assume you’re wearing a hat, a wool shirt, maybe mitts. assume you have just ate and have good circulation. assume there is no precipitation, the humidity is low and the temperature is around 5 celsius. make any necessary assumptions you feel are important.

