This is my opinion.
Main developer has changed from V1.7. And, release is late. The current development version there are some issues. If you do not plan to use existing plugins, it is also possible to upgrade when the stable version of V1.7 has been released in future. However, follow-up of plugins take time. So, V1.7 to help in actual use (including plugins) will be much later.
If you will publish Q2A site with server on the Internet, you should select V1.6.3.