I would think a full tower is more useful for water cooling, and huge amounts of kit eg SLI or Crossfire graphics card setups. Although some people may prefer the larger size of a full ATX case as I would assume they were easier to work on having more room, also it could well come down to prefering the looks of a bigger case.
The Antec 300 is a nice budget mid tower, but can't really be compared to the much more expensive Antec 1200 which I'm not even sure is on sale anymore other than second hand.
Anyway if your looking for a new case you will most likely want a good mid tower so look into something like a Coolermaster 690 II, HAF 912, etc. If your solely interested in Antec though, they have actually released a new case the Antec 100, which I think is the replacement of the 300.