The latter. It always helps if the staff have a clue and the fish are healthy to start
Discus require a mature tank, so after it's cycled (i.e. Ammonia and Nitr
ite have dropped to 0 in 12 hours after adding to 5ppm, or remaining at constant zero's if you fish-in cycle) you want to add your dither fish, or some temperary inhabitants, for about 6 months and forget that it's a Discus tank
Discus are widely considered hard to keep. This is mainly down to keeper igorance. Advanced, mebe, but difficult, no, not if you have researched them proerly and know their care requirements very well

Spend the 6 months you must spend waiting for the tank to mature before adding them to your tank researching whenever you get a chance. When you feel more confident about them, start trying to help people with Discus on forums. Make it clear that you don't yet keep them, just say what you would do. When other people that keep them keep comming in and saying yes, good advice/idea, you are ready to try them. If you keep being corrected, don't be disheartened, look on it as a chance to realise more research is needed before you jump in at the deap end

If you aren't well researched before getting Discus and don't have an established tank for them, you will likely loose them
Usualy, you aim for at least 18" tall, 48" long and 15" wide for a tank for Discus. If length is lacking a bit though, you can make up for it with a wider tank and clever aquascaping to break-up the lines of sight

It's best to try to go with fish at least 10cm long, and to start off in a bare tank
HTH
Rabbut