I personally like the samsung, I have the samsung galaxy s, and I've seen pictures of the samsung galaxy s2. I believe that the samsung galaxy series of phones are superior. Voice quality, processor speed, hardware capabilities, screen resolution, etc. are all great, I've never had an issue with any of it. The android market isn't as large as the App store, but at the same time, it's ever growing. All of the main apps that most people have on iPhones, people on Androids have the same if not a very comparable substitute.
Although I do like the iPhones, I guess I'm just not an Apple guy, and that's why I went for the android based phone.
Another thing, the galaxy s2 has a dual core processor with tons of ram and storage, I just think processor wise, it'll be able to run multiple applications at once. Gaming wise, it won't be as good as the sony ericson but still will be better than the iPhone.