Hi Justin. I'm building a Harrison and I'm happy with the kit so far. If I was paying for a 'turn key' I'd probably want regular access to the car during the build phase, so I'd be looking for something local, such as the Python.
The Python I believe uses a tubular frame and also has a good reputation on the track - so much so that Michael Schumacher bought himself one! See below for more info.
Cheers
Paul