Generally I advise a headset for voice applications like HamSphere. You will get the best results, the mic is close to the mouth and you avoid any "room-reverb" and background noises from the room. The modulation/sound is the best you can get and you don't need higher mic-level at the transceiver.
All build-in microphones on computers are only a makeshift/workaround and you are never close enough to it.
You get headsets for only a few Euros/Dollars (or whatever in Currency) and that's enough for HamSphere.
I always get a Radio 5 around the world with a 15,- Euros headset. :-) Mic Level just on 2 and always the same distance to the mouth.
73 and good DX from Jörg :-)
Bochum / Germany