I don't have the Express, just the Spider so I can't compare.
I got this one because it's low profile (easier to hide from the wind?) and seems to have a better windscreen.
As for the different burn times, my guess is that it's due to the fuel line. Pressure loss flowing thru the line? I don't know for sure though.
Personally I never (or rarely) run a burner full blast anyways (seems so wasteful of fuel) so I'd probably get similar burn times with either. Again, I don't know for sure since I don't have both.