On www.Flickr.com , there are 254 438 pictures of pizza but only 45 103 pictures of hamburger. At www.picasaweb.google.com , there are 129 218 pictures of pizza and only 10 706 pictures of hamburger.
Conclusion, pizzas are much more photogenic and Flickr is way more popular.
However, beer is king on both sites, 895 514 pictures of beer at www.flickr.com but only 171 159 at the more sober www.picasaweb.google.com .
Interestingly, there are only 27,312 pictures of cerveza at Flickr, and half as much at Picasa.
Vin is three times as popular as bière at Flickr. Wine is only 60% as popular as beer on that site.
The most visited city in the world, Paris, proves it with 2.9 million pictures on Flickr and, curiously, 3 million at www.picasaweb.google.com, the only search word I found where Picasa beets Flickr.
I'm happy to report that Picasa has 34 655 pictures of sheep compared to Flrickr's, yawn, 205 836. And on that note, zzzzzzzzzz.