Only you can decide if the price difference is worth the cost to you. What features are different? Do those differences matter to you? Are those differences worth the extra expense to you? Done.
FlickFreak
No. The R646 is significantly brighter for more impactful HDR, has better local dimming and has a 120Hz panel (vs 60Hz on the R546) for better motion with more sources.
Only you can decide if the price difference is worth the cost to you. What features are different? Do those differences matter to you? Are those differences worth the extra expense to you? Done.