It's not a negotiation of the tax rate, but of the tax status of the company. The tax rate (after tax) is fixed in all cantons and at federal level also. What changes with the tax status, is the taxable base. Therefore, the effective tax rate is lower if you reduce the tax base.

I don't want to make self-publicity, and I don't want the administrator to delete this post, but as everything is explained on my website, I don't see why I should explain everything again... you will find answers to your questions here http://www.dsconsulting.ch/?q=en/companies and there http://www.dsconsulting.ch/?q=en/node/34

Once again, I have no purpose to make publicity for my services, but I have explained it in detail there...

Regards