People have this funny way of arguing over if writing things or speaking them is more persuasive. Personally I think that, depending upon the topic, they are more or less equal. Yes, the conveying of emotions may be limited when it comes to writing, but if you word things right it really isn't. There's a reason newspapers and various other things can incite riots simply from putting a few emotionally charged words into an article. Some words have strong connotative meanings, ones that override the dictionary definition. Such things may vary from culture to culture, even person to person, but there is still that meaning buried deep inside there. While saying 'Man retrieves cat from tree' may not be so enticing, stating 'Man rescues pet from tree' gives it a bit more meaning. Retrieves compared to rescues, and pet compared to simply cat, is enough to give more than the simple facts do. Little words like that, when used correctly, can evoke a response.
Voice, too, has its pluses, of course. You can hear the emotion, feel it, without any added benefit of emotional words; of course adding those only drives the point home. You can hear if someone is near to tears or simply passionate about an issue, the changing tones and octaves of one's voice can lead to just as big a reaction as written words. We may generally take our voices for granted when it comes to this, but it is true. And some people have simply wonderful voices that make it so it is most certainly better that they speak things than write them.
In Second Life, you do not have but so much of a choice. Sure, you can opt for using voice, but that doesn't always means it'll work or that others even can hear you. The generally used media would be typed words, which, of course, is usually accompanied by an emoticon, a simple 'lol', or some emote depending on what is going on. Those various additions you don't see in much besides casual conversation, can add to things as well. It does leave the chance for people to misconstrue meanings, which is probably why the additions are relied upon, but you can still get a point across. Really, I think that we feel a need to use those other bits than 'just' words because we don't want to have someone misunderstand since they cannot hear us nor see our facial expressions.
Even when you use your voice, too, if you, perhaps, are more of a monotone person, you may rely more heavily on your facial expression and hand gestures. Words aren't always enough to get a point across with either medium, but they are a good base and can do some damage when necessary. So much ill will can be caused because of a carefully placed word here and there, in both lives, with voice or written things. There's a reason drama is abound in SL.
Both ways have their upsides, but they also have their downsides. As I mentioned, the downside to writing is it is easier to misunderstand, but with actually speaking...well, you may stumble over your own words more often or you might not be able to give as educated sounding an answering and instead flail your hands about trying to explain the word you forgot (I know I do that often enough). I know that sometimes my smart sounding words don't make it form my brain to my tongue...and then my tongue does all this stuff that I swear I didn't tell it to do; I'm pretty much convinced it has a mind of its own half the time. But when I'm typing I could, in theory, look words up. I don't personally, because I'm lazy and I have a backup not as smart word anyway when my brain just draws a blank. Or I just describe something. I admit to doing so in both speaking in writing; of course I can't use my hands in the latter to 'shape out' what it is I'm talking about, so if I want to give a timely response, I have to revert to simple description like 'the wood thing holding the awning up'. But for people who are a bit less lazy, they may look such things up and be able to give a halfways dignified response, whereas if they were speaking they'd have to do something else more than likely.
It really depends on what you want to get across and to how many people if voice or writing is the best way to go. If you want people to hear things exactly how you do, then voice is clearly what you want. But if you want to get a point across and call it a day, perhaps writing would be more the way to go. Either way, it is mostly the wording, and the extra add-ons, that do count.
And, as promised, my spoken version...please be kind... If you hear water running in the background, sorry, my fish tank. I also realize I'm stuttering and pausing, but I'm keeping it that way, since my point is general speaking and writing, not practiced and manicured. So...hope you put up with it and enjoy :)
Oh, and, of course, feel free to listen/read at the same time. There are pics, and it's on youtube, but only because I couldn't get this up here without going through movie maker and youtube >.>