We are using YSlow application and Fire Fox 6
Talking about the comparison of template of those companies:

• YOOtheme with Revista
• Rockettheme with Clarion
• Shape5 with Cyan
• YouJoomla with YouRetro
• Gavick with eSport
• JoomlaXTC with Barista

YOOtheme has just release Revista - The Joomla! Template on Febuary 2012. It is so clean and has a functional outlook with many choices for customizeable layout. With 22 background, three speacial wrapper options, a very uquide layout which has square shape, Revista will meet your need. It is built with Warp6 theme framework, HTML5 markup, CSS3 features and jQuery. If you are looking for a theme to fit your news or magazine page or your company website, Revista is the one. 

Since they launched YOOtheme back in 2007 they've used the website design for almost 5 years now. The thought it's time for a change and this summer YOOtheme started to work on a new website. After months of careful research, planning and development they are delighted to present the new website. Everything has changed from the design, navigation, downloads, documentation to the support system. Everything has improved and become much easier as well. Also all product pages have been redesigned to give a better understanding all products. This blog post will shed some light on the new features, content and the many new things to explore.