One major difference between Google and facebook is that Google sells your eyeballs to advertisers, facebook sells your information.
Whether you think that makes a large ethical difference is up to you, but the practical implications are significant -- essentially, Google acts as a black box in between advertisers and users, which is a system I massively prefer. Facebook will literally sell your name and address. I think that this is a significant improvement.
Of course, the other point is the question of trust. Can people trust Google? Maybe. I do, but I'm very careful about it, and I believe a lot of other people are too. The moment they start locking down services or locking in users, or the moment I actually find them doing something 'evil' (and no, accidentally leaving Kismet on a default setting does not count) I'm leaving them completely. Facebook, however, I don't trust at all with anything. That's trickier, since I live in a different city from where I grew up and a lot of my friends still live, and frankly facebook is in common usage, but then it's a trade off. I definitely don't put anything on facebook that I wouldn't say on national TV.
Another reason Google is in my good books, at least, is because they look at the long term. They want more people browsing the web as a general business goal, so they develop an awesome browser -- not necessarily to win the browser wars, but to make all browsers better. Then they also make it open source. Then they build driverless cars. Then they provide the best free mapping system in the world. Then they add satellite / overhead imagery to it.
Google might not be perfect, but they're by far the best multinational corporation I've ever come across.