In my opinion the 3G one is clearly the better option
If the Kindle weren't available when 3G then I wouldn't have bought one. True, wireless hotspots are not too hard to find but if you're in a hotel that requires you to connect to the network then open your browser to authenticate then you're out of luck as the Kindle can't do that.
I'm a frequent business traveller so I like the way I can get my daily newspaper 'delivered' every morning no matter where in the world I am without having the mess about finding a wireless hotspot. Turn the Kindle on and within a minute or two there's my newspaper.
Even if I weren't a frequent traveller I'd still have goen for the 3G version if only to get around the annoyance of being on holiday, finishing all your books and wanting something else to read. A couple of weeks ago I was in Munich (oh how I love the Oktoberfest) and while waiting for my flight back to Heathrow I finished my last book so without any hassle I went on the Kindle store from my Kindle and downloaded a book.
Global 3G is one of the main differentiators for me between this and other eBook readers.
My only gripe is that the directional keypad has a thin border on it so with my fat fingers I often push the central button when trying to push a directional button. A minor annoyance to what is otherwise an excellent device.