markdi,
i had a R3J 1watt put into my arc LS1 at stock current and a fraen and it is definitely brighter than before, the LSH-S has problably an M or N bin and your TWOH has more lumen capacity at the same current, plus you will get longer runtime due to lower Vf. if you use your LSH-S alot then i would recommend swapping out the existing LED for the TWOH, and like Billson said, you could also raise the current for more brightness but runtime will decrease.