The EE / CI way of passing information between pages

I’m developing yet another search module for EE. At the moment my solution for passing the query string from the search page to the results page is to append it as a get parameter on the URL when I redirect. This required an obscure chance to the config file, so I’m guessing it’s not The Normal Way of Doing Things around here. Perhaps someone could give me some insight on the relative merits of the alternatives I can think of (or even some new alternatives):

(1) Pass the query string as a segment in the URL

(2) Store the query in the database a la EllisLabs Search

At the moment the module is too lightweight for (2)… no search caching, authorisation, flood protection etc going on at the moment. (1) is interesting though - are there SEO or other good web design reasons for doing it that way?