(All IMO, of course.)

Being in shape is the key, regardless of the weight carried. Heavy isn't necessarily better either--it's just heavier. Reliability is more a question of design and appropriate use rather than materials. If you know the limitations of a piece of gear and how to use it correctly, anything is reliable.

I have five of everything because I used to manage a backpacking shop (which is like letting a drunk tend bar). If backpacking, I'll always choose the lightest item that will do the job at hand, which varies.

My three-season long-distance pack weight is 15 pounds before food and water, and that has seen me comfortably along 400 miles of the Appalachian Trail. On weekend trips I might push the envelope and get under 10 pounds, or go the other way and carry luxury/winter items (white gas vs. alcohol stove) that jack it up to 25. In higher mountains or off-trail, my pack obviously weighs more. My day-hiking gear weighs more than my backpacking load just to keep me in shape. I also try to get out occasionally and bivy with my day load, which keeps me honest.

None of this matters if I let myself get out of shape. In-shape with a heavy pack is fine, but in-shape with a light pack is a blast. I can run a quick mile with my pack on (which I've done to get off a ridge when a sudden storm blows up out of a blue sky), do 12 miles before lunch and snooze the afternoon away, or just keep going and rip off 30 miles without paying for it the next day.

The difference between a 3-minute boil (white gas) vs. 6-minutes (alcohol) usually doesn't matter because I'm not out there to count minutes. Your mileage may vary :-]