Any version from the stable branch is going to be more up to date than a downloaded one after a few days, as it is where the correction for bugs end up first. Beside, that's much more easier to manage than download, unpack, bla bla every new rc version.
Go for svn, the stable branch, unless you want to be close to the bleeding edge (trunk).
Thanks Xavier. The case is I'm waiting for a webfarm server. Because I don't have a lot of time I'm starting developing in local mode. When I will have a ready-to-go machine I will install a stable version. Do you think that if I develop (templatee, new classes and extensions) in rc1 version (which have an installer) there will be problems later?
A little warning about using the stable branch directly from svn: sometimes new bugs get introduced on the stable branches. The latest releases of all stable branches were affected by nasty bugs in the e-mail system, causing e-mails not to be send anymore. Of course you get the fixes sooner if you use the stable branch directly from svn, but you will also get new bugs sooner...