Pedants aside, i think it's pretty easy to make an educated guess.
Maglite have better market penetration, go into any hardware store, and theres a good chance they'll have a rack of Maglites.
They also have brand recognition sewn up.
Ask Joe Public to name a flashlight brand, and 9 times out of 10 they'll say "Maglite".
This is true the world over.
Then there's the R&D; we all know Surefire spends a considerable sum on developing new lights as well as highly specialized designs intended for limited markets. As far as i'm aware Maglite spent all their R&D on finding ways to make it cheaper to manufacture their existing design (until the MagLeds came along), so they managed to milk profits from one product for over 20 years; this can only be a good thing as far as the bottom line is concerned.
On the other hand, Surefire has government contracts, and we all know how lucrative those can be.
But if i were a gambling man, i'd put my money on Maglite being "bigger" whatever way you want to define "bigger".