I use Socialize as my main FB app. I also have Fast Facebook installed and I'm trying that too. Either one of these are a major improvement over the "official" app. FF still needs some polish with ui and a few bug fixes but overall it's a good app. With a few improvements it could replace Socialize for me.
I use a browser. When I had the Facebook app installed, I started noticing "friend suggestions" that were very obviously harvested from my contacts list. My boss's daughter, my ex... And that was with the contact integration disabled.