Well, I don’t much care for Xanga. It is far too busy, too many ads, especially annoying on the personal page. LiveJournal has ads also, which I have removed for less than a cup of coffee. Xanga however states that ads will still be visible on the user’s private pages when using a premium account… just not on your actual blog page.
Also, too many additions of little extras that really aren’t necessary.
LiveJournal is still ahead as far as nice clean themes, and ease of posting, and ease of changing themes. Tumblr I guess has a bit of a learning curve, but I’m figuring it out. The Theme Garden doesn’t have categories, other than recent, popular, and featured. Colour, style or layout categories would be nice. However I love that tumblr is ad free. It offers all that is needed with the ability to add in some sidebars if you know a bit of html (I don’t, however my current theme had a few sidebars so I just added more. STILL trying to figure out how to get them from just the Random [In MY Head] page to the main page but meh… small potatoes.)
Social-wise, well my blog posts are rather dull, so I don’t imagine people will be flocking to read them. I’ll give it a few weeks of cross posting on all three and see how it goes.