If would like to make sure we are talking in the same terms:
I equate
-Ich as Cryptocaryon; salt size white spot on fina dn skin first before gets tot he gills
-Oodinium as smaller than salt size, lind of like powder size white spot usually attack the gills first
If we have the same definitionoodinium, then most authoritive sites, including about.com, couple marine pharmacuetical sites, will claim oodinium kills fish faster as they attack the gill first and if we do not notice our fish in a short period of time, they die before we even have the chance to cure them. Even though, copper is very effective towards oodinium, most of the time, fighting oodinium is a loosing battle.
If we have the same definition of ich, then most authoritive sites including about.com and couple pharmaceutical company, will claim ich progresses slower than oodinium and is easiler to detect in the early stage as they are more readily found on the outside skin of fish. Unfortunately, even copper is not too effective against it. So treatment is a hard long battle.
Can coral or rock or even water carry parasites? Yes they can. They can carry the free swimming form and the dormant form that fallen off from the host. Therefore, no matter it's fish, inverts, coral nor rock, don't put transport water into your tank. Minimize it to the lowest possible.
QT is yet another hard to carry out topic. Many people wishing to keep the color of the coral and thus will not dip them. As someone mentioned earlier, to maintain a seperate system that is good enough to support corals, especially SPS, for long enough time of safe QTing is even rarer to be seen.