Dan, your link seems to be broken, or Home Depot got rid of the item after you posted.
John makes a very good point about commercial vs. hobby use of tools. I think if you are going to do multiple projects, and plan on ever doing any other finish spraying, a good quality gun is the way to go. Finishing is your final step in the journey, I know I wouldn't want all my hard work flushed down the toilet by a junk finish being sprayed on. Just my thoughts.
I've used both siphon and gravity. I've found the gravity feed guns are a lot easier to keep clean and service. The siphon ones are working against physics right from the start and sometimes require you to thin your material down to get a good flow.