TCL 4 Series is a budget-friendly 4K UHD TV, while the 6 Series is a more premium model that offers better picture quality and sound.
The 6 Series also has Roku built-in, which gives you access to over 500,000 streaming apps and services.
If you're looking for the best value, the 4 Series is a great choice. If you're willing to spend a bit more for a better overall experience, the 6 Series is the way to go.