A big way it differs from Facebook is you can add someone as a contact to any of your Circles without them adding you as a contact. Circles are a way of organizing your contacts. You can choose Circles like Friends, Family, Business, etc. When you post items, you can determine which Circles are able to see your posts. People that are in a Circle of yours can see they are in one of your Circles. They will not know which one or who is in that Circle. If you have someone in your Circle but they do not have you in one of theirs, you can see what they post subject to their sharing restrictions. For those using Facebook, think of Circles as the Lists you may have for Facebook friends. Your Facebook friends do not know what list if any you have them on. You also may share or not share posts with Lists. Circles are considered a strong selling point of Google+. They are easier and more user friendly to use then than Facebook Lists. Further, there are those who use Facebook and do not realize that Facebook has a similar feature as well.
Another feature of Google+ is Hangouts. Hangouts are where up to 10 people can have a group video chat. For this you will need to download and install the free Google Voice and Video Chat plugin for your computer.
Sparks is another feature. Your Sparks are only visible to you. This is where you identify subjects of interest to you. You get to see streams based upon your interests. Without you putting your interests in your profile, there is not a way for others to see what your interests may be. Facebook allows you to share pages, groups that you belong to. There currently is not an option like this in Google+. This link may be of help in getting a further understanding of Sparks.
Perhaps the biggest selling point is privacy. Not only is Google+ more private, it is a lot easier to manage privacy on Google+ than Facebook. It is easy to determine who you wish to see your posts and personal information.
Will items in Google+ get rated better in a Google search? That is for Google to decide. I would hope that the protocols used in a Google search ranking continue to be used here so as to be consistent.
Keep in mind that Google+ is a work in process. Improvements and enhancements are being made on an ongoing basis and as I mentioned it is easier to share interests using Facebook. It is expected that Google+ will be opened to all by the end of July. You are able to share photos and video just like Facebook. The quality of pictures shared in Google+ is better. It will be interesting to see how Google will integrate Google+ with its other products as well. Right now Google is by and large discouraging business use of its new program. When it is ready for business use what will it be like? The jury is out and Facebook may have some heavy competition to contend with. Then again with LinkedIn moving more toward subscription services maybe the niche of Google+ will be a professional networking site. My personal opinion is LinkedIn should worry more than Facebook. Facebook, LinkedIn and Twitter for that matter have not gotten where they are by standing still. I would expect them to make changes to their product as well. Time will tell how it all plays out.