Blade Vs. Rackmount Vs. Tower Servers

We have always used standalone servers (towers/workstations). Does it make sense to use Blades or Rackmount systems? We're looking to purchase several components together in the near future and want to spend the money wisely.

Blade server notes

A few articles turned up via Google:

• Why Do Rack Servers Persist When Blade Servers Are Better? - Article from Feb. 2005
• To blade, or not to blade? - June 2007 article
• http://wikibon.org/Portal:Storage - may contain useful information, after parsing the business speak
• http://blogs.sun.com/marchamilton/entry/sun_s_new_modular_blade