'Skiing is easy to learn but hard to master, Snowboarding is hard to learn but easier to master'.
You're likely to fall over more learning to snowboard but will become competent and able to carve down the mountain faster.
Other elements to consider, Skiers are usually able to go faster than snowboarders down the hill. Snowboarders will have to unstrap and strap into their back binding when entering and exiting the chairlifts. Snowboarders have many more easy trick options available. I know hardly any skiers that can do any tricks, most of my competent snowboarding friends are able to at least do small jumps of sidehits (mounds of snow on the sides of the slope).
I'm a passionate snowboarder and cannot recommend the sport highly enough, there is just no feeling like riding down fresh powder snow on a cool winters morning!