The RLT is similar to a stable platform type design which allows the fork to mimick a rigid fork during climbs whereas the RLC is fully active at all times. With the RLT you're going to have a much stiffer ride than with the RLC and the RLT is lighter. In essence, the RLT is truly an XC fork whereas teh RLC is much better suited for more aggressive riding.
If you're a hardcore gram counting, spandex wearing, lung burning, 150 pound demon then you'll probably want to go with the RLT but, if you're like most of us who want plushness and control over rigity in our forks, then go for the RLC.
P.S. I used to have a 100RL (similiar to the RLC) until I bought my TALUS and I loved that fork.