I generally have just typing convos but when I do use the Webcam it's with people that I know and trust. Works best with people that get distracted easily like me cause then If I take a bit to reply they understand xD
It depends on the person, for me, and the reason we're contacting each other If we have something specific to talk about, I'm okay with skype calls (I don't own a webcam but that'd be okay too), but if we're just chatting for no apparent reason I'd rather IM because I multi-task while I talk to people and it's awkward to try to listen to people while reading dA journals and shiz
It all depends on what else is going on... If I'm likely to get called away todo something or other, or if I've just left my laptop running text is probably easiest so that you can rely at a more convenient time.
Even though I love them phone call conversations, I'm always getting weird looks here when I start talking in English all of the sudden. So instant messages work best I guess. And you can pretend you're not there when you don't know what to write, so that's something.
I usually prefer IMs since I am considerably better at expressing myself over text than verbally. I do sometimes call or video call people I am very close to if I'm feeling lonely, but not often. (and video calling people while just typing back and fourth seems really awkward, ha ha XD)
Voice and video or voice only. I think the fact of speaking is crucial because it helps me to develop my skills towards english language. When you speak often with someone, even if you suck trying to speak a foreing language, helps much more than just learn how to talk with the guide of a teacher. Sorry for my english.