Between the Fs-i6 and flysky fs-th9x which would you say is more suited for a beginner with a tight budget who is starting out in fpv quads?

The flysky fs-th9x won't go the long way unless you upgrade it with a frsky module .
One of the flysky radios supports Sbus. I  recommend you go with radio with Sbus as most of the quad flight controller supports Sbus allowing you to fly smaller quads.

As I had earlier mentioned about my Transmitter for sale (turnigy 9xr with frsky djt module) it would go along way it supports Sbus and more channel mixing . The radio is for 6.5k but you'll still need to invest another 3 to 3.5k to get a 3s lipo to power it and also any frsky receiver.

At the end of the day which ever radio you buy it should fulfill all your requirements. The radio is one piece of hardware that doesn't change much in the hobby