SPS are small polyp stony corals and LPS are large polyp stony corals. Soft corals are in a class by themselves. As far as difficulty in keeping and greater demands, SPS are the hardest, LPS not quite as hard and softies are the easiest. Now, mind you that this is not necessarily always the case, but as far as i've experienced, this is the general rule. SPS seem to require the most light and best water parameters. I have ever had any success with SPS which i am sure is due to my lighting and the fact that I don't use ro/di water but iI've had pretty good luck with the LPS's that I have tried (green open brain, candy canes, scolymia, hammers and frogspawn). I did have an alveopora that did great for about 6 months then mysteriously died. That was a shame, it was an absolutely gorgeous coral. As far as softies, I have shrooms, ricordia, leathers, zoos and some others, although i've not had good luck lately with xenias. I have read that LPS and SPS don't do well with leathers that shed their skin. Seems that there is something fatal to lps and sps in the process of sheeding their skin. As far as the xenia, I think my problem is too high phosphates or to low nitrates. It sound stupid, but as soon as I got my nitrates down to 10 ppm and less, they tanked. If I was you, I would start with some shrooms, zoos and leathers/colts. They do great under less intense light and some I think prefer it. If anything I have said here is wrong, feel free to correct me anyone, cause lord knows, I don't know it all.