Drupal six or seven for a new job platform - or a different framework?

For a client we are going to build a platform for specialized artists where customers can find contractors. This involves building a job board, logins and profile pages for different roles, a quite complex admin interface for managing and charging the deals. We have now done the wireframes and specification, but are still not sure about which framework to use. Our currently most probable option is drupal, as there are a number of things already done, that we do not need to implement again:

- User administration, registration/login, roles, etc.
- Editable pages for non-html wizards
- standard theme for the backend
- good extensible module structure
- plugins for seo and the like

The first question I have: Drupal 7 is now in bbeta2, there are five critical bugs to go for the release candidate. Go live for the platform is planned this year. Should we go for Drupal six or seven?

Pro six:

- drupal six is stable
- drupal seven might not be stable on the day of the go live

Pro seven:

- nicer database abstraction layer
- client will have a lot more time until he needs to upgrade the next time which seems to be quite some work.

If you have other ideas for apt frameworks feel free to suggest them, but please keep in mind that we are most experienced with php, java and ruby.

Thanks a lot for your opinion!

To build on @Macros^ point: Drupal 5 is still being supported and patched (this will stop when D7 is released), so there's some reasonable assumption that D6 will be around a while as well. D7 has been in the 'we are about to release it' stage for too long now and with every development snapshot something has changed that affects functionality (I've tested just about every one of them). I am still deploying D6 on new installations and will continue to do so.

^ +1 for you btw :)

It looks like one of the main drivers behind you choosing Drupal (and is with most people choosing it) is the availability of a module to do most things you could want in a site. If you go with 7 before it's official release you may find that not only are you dealing with the possibility of bugs in the core, but you are working with betas or RCs of the modules you want. Many module developers who have stable v6 versions have pledged to have stable v7 versions ready for the day of release however are not able to guarantee this beforehand as code in the core may change.

If you are starting out with Drupal I would recommend going for v6 due to the wealth of knowledge and modules that is available and tested as you can then be fairly safe in the knowledge that your learning is not going to be hampered by a hard to track bug that is not of your doing. The core Drupal skills you will then develop will be transferrable to Drupal 7 and should assist is an upgrade once v7 and any associated modules are stable. The process may be a bit laborious however having a good working knowledge of Drupal will help in identifying any issues along the way.

I would go for Drupal 6. In this moment Drupal 7 may have a lot of issues that you must to upgrade. Drupal 6 have a lot of time of testing and it's proven that it is very stable.