As I just answered in your elderberry post, not all elderberries are edible yet they are all in the same genus, Sambucus. So, no. One hibiscus species does not equal another hibiscus species.

If you visit the Plants For a Future site (pfaf.org) a do a search for hibiscus, you will get a listing with the plants you are asking about. Read their edible and medicinal qualities. They are quite different.

FataMorgana

flowers from this plant family clear heat and some are moistening, don't know of any that cannot be used internally. this is the same family that gives us marshmallow and okra.

I tried your site & it would not search anything for me.
I did not find the two hibiscus in my Poisonous plant field guide.

http://en.wikipedia.org/wiki/Hibiscus

perhaps you can find what you are looking for here...scroll to the bottom and scroll on the species you want to know more about. neither of these two are poisonous and are in fact commonly used in herbal medicine, especially in summer to cool the body down.

That is what I thought, but I always check my:
Peterson Field Guide Venomous Animals & Poisonous Plants.
I started this when I taught wild craft & poisonous plants to Boy Scouts.My son will soon be an Eagle Scout!

I have Hibiscus syriacus.

Not saying you can't make tea from the other hibiscus but the H sabdariffa is the one that red zinger tea and the mexican drink flor de jamaica are made from. They have a very fleshy calyx that is very unlike the other hibiscus and that is what you make the tea from. I used to live in Hawaii and grew sabdariffa easily. Would preserve the calyces in syrup. They are spectacularly beautiful plunked into a champagne glass with champagne poured over them (makes the champagne pink and slightly fruity/tannic with bubbles rising from the red "flower") Tried to grow here and even with starting indoors early, the plant did not bear flowers before the frost. I think you will need a greenhouse to grow in this zone. The plants get pretty big (24-36" even in a 2 gallon pot) and need a lot of light so hard to grow indoors (tried to bring it in before frost and keep it alive but no success)

I've had difficulty overwintering H. sabdariffa as well. I suspect they resent everything about my house in the winter - colder, darker, and drier than they prefer.

They do start from seed easily if you want to grow them and seed is available from online seed vendors. Look for the name "roselle" since that is what the seed is often called in the catalogs.

FataMorgana