Google+ gives me the same opportunity to share updates with people outside of my social network--and the public at large--but without limiting the length of my post. Ultimately, though, this is not a black and white issue with a clear winner.
The Google+ approach is much more flexible, and allows for richer posts, but it can also cause more clutter. The Twitter system is genius in its simplicity, and it fills a unique niche thanks to that annoying 140-character limitation.
• Privacy. On Twitter, I have none. Well, almost none. It is possible to set my Twitter profile up as private where only those I allow are able to see my tweets. I can also just direct message (DM) someone who is following me for a private one on one chat. But, anything I tweet out the normal way is shared with the world--those who are following me will see my tweet in their stream, and anyone else who doesn't follow me can still find and see my tweet by searching Twitter.
Google+, on the other hand, straddles the fence between Twitter and Facebook and enables me to choose on a post by post basis whether the update should be share with the general public, or just my Circles, or just a specific Circle, or maybe even just designated individuals.
From my perspective, it seems like Mark Zuckerberg has not used Google+ at all. But, it's possible that he's posting 100 times a day, but just not sharing those posts with the general public, which means they don't show up for me.
• Audience. Twitter has roughly ten times the audience of Google+ right now. Yes, I realize that Google+ is still in limited "Field Trial" mode, and that it is not a fair comparison. But, even when Google+ launches to the general public, it will still have some catching up to do.
From a marketing or breaking news perspective, Twitter is a more valuable tool--and will continue to be more valuable for quite a while--because it offers a larger audience to broadcast to.
In the end, both Google+ and Twitter offer me the ability to follow others who aren't in my social network, as well as a platform for broadcasting my own updates to those outside my social network who choose to follow me, and to the general public.
I see the difference a little like comparing CNN Headline News to the main CNN channel--Twitter is Headline News and Google+ is CNN. Let me explain.
CNN is a great source of news, and devotes more time to investigating stories, talking with experts, presenting both sides, and diving deeper into the topic at hand. But, if I just want to know what is going on in the world right now, I would rather switch over to Headline News where I can just get the 30-second sound bites that basically announce the headlines and let me know what the breaking news is.
Similarly, both Google+ and Twitter are good sources of information, but Twitter is still better for just keeping up with breaking news and trending topics, while Google+ provides a platform for more comprehensive coverage of those same topics.