I see that there are a lot of web pages that offer creation of a site map for you... is one better then the other?
AFAIK the main thing is to just list all your pages so that google can find them easily. I think you get indexed easier that way. I doubt google cares how important you say a certain page is.
We use gSiteCreator and the default setting. Google likes the XML Sitemaps and processes them without errors.
I would recommend spending some time on the sitemap. Its one of the few ways that you can communicate with google and tell them about your website, all the pages and which ones are important. However, I wouldn't obsess over it. Its meant to be a tool not something that you spend hours and hours on each week.
I would recommend , this is better than the above said one, above one is not free for large sites but this is free and unlimited sitemap creation service.... http://discusshub.com/sitemap/
Well, the one that works great for our company, which has several websites and sitemaps, is A1 Sitemap by Micro-Sys. It's not free, but has many options for tweaking your sitemap, and it's very fast.