Encoded Urls Vs Not Encoded, Do spiders interpret them differently?

[Capites]

Hello
i need your help
We're doing some massive 301 redirections within our domain because of a change in technology here.

Our new URL formats are application/x-www-form-urlencoded compliant. If our URLs contain spaces, they will be replaced by a + sign for example. The old URLs weren't encoded that way.

The redirection won't encode the URLs based on the application/x-www-form-urlencoded MIME type. For example, let's say that we currently have the url:
www.domainexample.net/hello world.htm
it will be redirected to:
www.domainexample.net/cgi/hello world.htm

If you come visit our website, you'll find a link on the index page pointing to:
www.domainexample.net/cgi/hello+world.htm

My question is: will spiders be wise enough to realise that this is the exact same URL? I don't want to get a ""duplicate content"" penalty just because my redirect is not encoded the same way as my new live URL.

The redirect we're putting in place is to keep the traffic we get from our currently indexed URLs. We do get good traffic from search engines and we don't want to loose that!

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