Translation:There are more advantages than disadvantages.
In English, Gav-ol's version would be the most natural way to say this, IMO, unless there was an actual list and the 'ads' numbered greater than the 'disads'. Then I'd say 'outnumbered'.
I do understand we're here for Swedish, and that other answers are closer to the language we're translating from.
That said, it's nice to see Zmrzlina's suggestion of a preferable translation, thank you. :-)
Another very natural Swedish way of saying what you want to express is just Fördelarna överväger. I agree with Zmrzlina though that what you want to say is something different from what the Swedish sentence here says. Keep in mind that this Swedish sentence is just a sentence – it is not a set phrase. It really doesn't mean that the advantages are more important than the disadvantages – only that there's a larger number of them.
This sentence is supposed to be translated from Swedish into English, so if you got it as a listen and type exercise, the answer is simply that you have to type what the voice actually said.
On the reverse sentence, flera is an accepted answer, but it's not the best one. In principle, fler means 'more numerous' for countable things (as in 'there are more X than Y') and flera means 'several' (Jag har flera katter 'I have several cats' but jag har fler katter än du 'I have more cats than you) but especially in the spoken language we tend to use flera for both.
I believe "The disadvantages are more than the disadvantages" is a better translation than the one I was supposed to make out of given words: "There are more advantages than disadvantages." Since there was no "the," I chose "advantages are more than disadvantages.
If it's supposed to be "There are more advantages than disadvantages," why wouldn't the Swedish be "Det finns fler fördelar än nackdelar"? In other words, I think this translation is wrong and should be changed. :/
Just leaving this here: As devalanteriel wrote earlier in another discussion (https://forum.duolingo.com/comment/7756693) fördel is derived from "the first - and better - part of something you split in two" (för + del)
With regard to this, in nackdel "nack(e)" actually means neck/back of the head/scruff. Although, I have not found any source for is exact etymology so far.
I hope it helps others.