T20C2 MkII is smaller, has a variety of drop-in modules that allow for a huge flexibility in terms of beam profiles and has a ton of accessories. Popular drop-in modules include XR-E for maximum throw, XM-L for maximum flood and XP-G for balance. Drop-in modules with colored emitters are also on sale. If colored modules aren't your thing, you can also swap out the front bezel with color filters. Diffuser filter allows it to light up a wide area very evenly. It's a hardy light that can serve a variety of purpose, andI love it.
Predator, on the other hand, is a bit bigger, owing to the much deeper reflector that allows it to have an immense throw. In fact, it's one of the two pocketable tactical lights that offer a massive throw with XP-G emitter. (The other is the TD-15, which is slightly smaller but throws just as much. Even Maelstrom G5 can't match these two.) Aside from huge throw, Predator's main advantage would be its customizable UI and the presence of moonlight mode, allowing for preservation of night-adapted vision.