I don't know about most people but I have them both and they each have their own advantages and disadvantages.
The Spark Lite is smaller, lighter, can be used one-handed, and works great with cotton balls or equilivant tinder.
The Mag bar is bigger, heavier, requires two hands and works great with cotton balls or equilivant tinder.
I have never had much luck with the mag bar shavings. They blow away and burn up quickly.
Just my 2-cents worth
Tom