For the Google Maps question: The size of the google map won't affect the load time of the page. Google maps sit in iframes and are loaded from Google's servers asynchronously after the main page. The worst things that could happen from having a larger iframe containing more content are:
- a slightly longer moment where the iframe's content is not fully loaded - but it's a background element anyway, so users' attention will be on the page content and their use of the site won't be slowed down.
- slightly higher bandwidth usage. If this was the design for a mobile site intended to be used frequently on the go, or if it was targeted at a market (e.g. 3rd world) with access only to slow connections, this might be a concern - but that doesn't look like a factor here.
Bottom line - any difference it made would be very small, and wouldn't slow the loading of the main site content. But like everything else in a site it's something that should be tested. If you're very concerned, consider asking on a site that is more technically oriented (webmasters.stackexchange or stackoverflow.com?)
As for the design choosing question, see comments.