Would someone mind explaining "zero loss" shifters?
As Heluv explained above, zeroloss does seem to make a nice difference to the left-hand/front shifting, which is probably why it's been incorporated across the line. The differences in the RH/rear shifting are harder to notice.
One of the biggest reasons for this is that you only get a true 'zero loss' shift from the first shift position. On the front, this means from the little ring (you will have some slack to get out of the line when you're shifting from the big-ring's inner trim position to the outmost position), but on the rear, it means that you only have a completely slack-free shift when coming off the 11 (or 12 if that's your smallest cog). All other shifts will have some slack, a few mm of free movement, at the start of them.
I believe the RH/rear shifting on Red is still a bit shorter-throw thereafter, but it's very tough to notice that difference. Certainly the internals are a bit different though too, as I haven't ever heard of anyone having the RH double-tap paddle break off on a Red shifter, whereas it did seem to be happening quite a bit for both Force and Rival a while back.
Finally, with regards to Apex, the lever blades are alloy and the shift bodies are a lower composite material versus Force/Rival (Red is one step up in this category). The Apex crank is a non OCT (ie. hollow) design, so it's heavier then even Rival in that category (without the massive stiffness numbers Rival offers), and the brakes are long-reach for larger tires... but you still have to love how 'concentrated' the SRAM line-up is. I can't imagine any Shimano sponsored pros ever considering running Tiagra for an important mountain stage!!