In reply to Rob Naylor: Oh FFS...
1) There are different Quasars available now. There is the Endurance Quasar, which is heavier, and the Ultra Quasar, which is lighter, QED!
2) The modern Quasars have a much improved flysheet, (Watershed?) which IIRC is nylon with a durable PU nylon coated inner and a silicone elastomer outer. It's not possible to tape silicon elastomer, which is why all SE only tent flys come with seam sealer for us to dick around attempting to seal ourselves. So TN put PU on the inside, to allow seam sealing and stop us moaning about having to seal seams ourselves.
3) The difference between the Ultra and Endurance ranges is the weight of the nylon in the fly. Ultra flys are ripstop, and Endurance flys are a heavier weight with better UV resistance (presumably you have to fry more, thicker fibres before they lose strength).
4) I think the SE coatings inherently improve UV resistance too. As far as I know the external SE coating is a relatively recent upgrade and the tents described above may have predated this.
So, the nub is, flysheets now are better than they were a few years ago - but are still to a greater or lesser extent will get fried during prolonged use in intent sunlight. Saunders flysheets can be SE coated only, whilst the heavier grade ones are PU again - with taped seams.
So instead of comparing one tent fly with another, compare flys made of the same material with the same coatings....