They all veritably offer the same features....chat, free call (video), etc. I guess it just matters what you've used and grown accustomed to first.
I prefer (use), skype and I think it's superior now that they offer skype phones.
My g/f recently went to Europe on business for a few days and we both also have skype phones and accts. so we talk whenever, where ever for however long we want no charge and not tethered to a computer.
I also, keep up with friends, business associates and family whenever I need to talk internationally with skype.