Please correct me if I'm wrong, but isn't the SBT70 just a SBT90 with a phosphor circle and a masking over the rest of the blue LED? The only advantage right now is it is available in 1 higher flux bin than the SBT90. But it's going to be a more blue color.
The XR-E is the classic thrower LED, and still quite capable, but it's output limited to 3-400 Lumens with perfect thermal path and overdrive. It is especially good with the EZ900 .9mm sq. The XP-G2 can be overdriven to over 800 lumens and the die is still small at 3.45, I believe. The tiny die of the XP-C may be the best thrower of them all if it could be pushed hard enough, but I don't know if can be pushed too much over 100 lumens or so.
I think it depends on how many lumens you're looking for then go from there. My best LED throwers use the XP-G2 driven to 3.3A and SBT90 at 13A. They have very different outputs but both will light up things far away. If you are using an aspheric like on the DEFT, don't use anything bigger than the XP-G2. With a much bigger lens the bigger dies would work but the light would be huge.
As long as drive over a watt, I haven't bought an xp-c that I didn't like. Maybe the coleman xpc headlamp, I hated because it was underdriven and supershallow refector which was bare respectable enough to be called a reflector. The color and throw of the xpc are wonderful.
The down side on most xpc lights is the poor driver and power supply. The Rayvac indestructible xpc 2 aa light has a good driver, and 4 hour of near flat runtime with 9000 lux, if I remember--with a killer price. In many ways (like wristlighting dry wall repair), I like it better than my 18650 regulated xpg2, which has 1/4th the throw.
Though overall, I would rather a larger battery pack, good reflector, and an xpg2. [XML's can throw at lower current, but need a large reflector (often xml heads come so heavy (for heat dissipation at the possible high drive levels) that many occupations with heavy xml light housing are not practical--wristlight and headlamp.]
