All LPS are generally harder to keep than most softies, but if you've got the lighting and water parameters for it, then great.
Out of the ones you've suggested, bubble corals can be delicate in that they're easily physically damaged, and don't look that great IMO.
Torch corals can sting either you, or nearby corals quite badly, but are very rewarding to keep. Hammer corals are very similar, maybe a little less stingy, but will still desimate any softies or most other stonies nearby...
From your current tank size and stocking it looks like your tank is new, if that's not the case, then it sounds like a low nutrient tank which could be ideal. If it is new, then you might be best waiting longer before spending money on stony corals.
5 T5s is the bare minimum for stonies too. So only go for ones which are low light requirement, your currently lighting wouldn't even be described as medium.
Good luck, Mike.