Standing is much better not only is it more productive, but 20 to 50 more calories can be burned an hour by standing compared to sitting. I've been using a standing desk for the past few weeks and I've found that I can do work much easier and faster than when I was just sitting down, I can also work for much longer since my energy levels are boosted. At first it bothered my feet but I after a few days I got used to standing up for hours at a time.
If you want to get a standing desk without spending large sums of money you can easily convert an existing desk by using push blocks or concrete cinder blocks. Or you can make a desk by making a wooden saw horse desk, and having the wood cut to put it at a level good for your height.
When it comes to health related topics, there's always going to be people claiming that something won't work even when there not only studies by Universities confirming the results as well as people that have benefited from it. The University of Chester did an experiment and found that standing up burned an average of .7 calorie per minute more than sitting.