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Should I use CDN or not?

I was doing some comparison of home page loading of my company's website and one competitor's homepage loading. The competitor website loads in a snap and ours take some secs before it shows up. Here are some of the stats from YSlow for mine and competitor's site.










Now as I can see that competitor is making more images/JS then my company's site but it loads in a snap. I can notice three differences
  1. They are using a CDN so images are being downloaded from a local server near Dallas
  2. Their total download size for Java scripts and image are 1/3 then ours.
  3. ours is HTTPS and their site is HTTP. We can't change to HTTP as we cater to SMB and security transmission is a key for us.
I am working with the team to reduce the size of Javascript download and cut it by half. Earlier we were using YUI for tree and ExtJS for table. We recently moved to ExtJS tree as it performs much better then YUI in IE and when you have large no of  children nodes. There are few remaining pieces of code that still rely on YUI so removing them will cut the size of JS download by half. The size of images are also double the size of competitor mainly because our website has went through so many revisions that the sprites are becoming Fatty and we are not removing unused images out of those, plus some stupid decisions by developers to create a new sprite with common images has also caused issues. I had already tried smushing images and got the maximum juice out of them I guess I will have to go through a big cleanup.

But in the interim I am in dilemma to use CDN or not? Even locally within the intranet the home page load is sluggish so it has to be the size of download. Will try to reduce the size of download and see the timings?  If I can match the competitor's Kilobytes downloaded then I can think of using the CDN or not.

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