If not then I'm not sure how much useful help you'll get here (this is the TurnKey Linux forums). You may be better off asking your questions on the Magento forums.

Anyway, all things being equal, 2 separate Magento running on the same server should run similarly under similar circumstance (e.g. similar load etc). Obviously content will have some influence but unless the 'slow' site has significantly more load then what you mention seems more likely a config issue (besides assuming they are running on the same apache then even additional load should make both sites slow...).

So perhaps your redirect is the issue; or perhaps something else. Regardless it seems to me that it would be worth fixing your redirect. Then I suggest that you do some further testing and benchmarking and do some research on apache optimisation (assuming that you are using the Apache webserver).