To be honest HT does not make any real difference that I could see.. its not really worth the effort of the upgrade if you are happy in RH7.3..
The potential benefits of hyperthreading are -extremely- application dependent. That they do or don't help for one person or application has pretty much zero bearing on their utility for another.
For more about hyperthreading, I recommend the following article:
http://arstechnica.com/paedia/h/hyperthreading/hyperthreading-1.html
