Mail order fixed

Butted tubing is not as strong, but it removes metal where it doesn't NEED to be as strong on a typical bike. there is very little latteral stress on the top tube of a bike, the only stress is compression down the length of a tube, so a butted tube which is thinner in the middle is less strong to lateral stress than plane gauge, but the bike (in normal use) will rarely see any latteral stress so in use it will appear to be as strong, Crash however and put stress on the bike in ways the designer did not intend and you will soon find butted tubes dent and fold much quicker than plain gauge.

You can use larger diameter tube which is stiffer, but then you lose the springy compliance of the frame and the ride becomes harsh.

Gussets are a strange addition to frames, they have to be very well designed, look at some of the DMR frames of old and the gusset actually focuses the stress on a small area of the tube, they cause localised cracking (usually at the end of the gusset where the corner of it is welded to the tube, the heat of the welding making the metal more brittle doesn't help here) and generally do little for the actual strength of the frame. But if done correctly they can add a lot of strength, although if you design the frame with the correct tubes then gussets should not really be necessary for all but the most hardcore users.

If I wanted a real solid bomb proof hack bike I would probably look at plain gauge tubing for a number of reasons, overall strength (especially for when its chained up and gets knocked about, and I fall off it) and cost, especially in the far east plain gauge steel is much cheaper (probably why charge are using it, there is much less wastage in mass production). if I wanted a light weight road bike that I would take more care of then butted would be my choice.