Before start I want to tell you all that the Asus is not a Chinese company, ASUS is a Taiwan-based, multinational computer hardware and consumer electronics company that was established in 1989.
Boht the laptops are best in there own, but let me know that the laptops is almost similar to one another.
If your are searching for big display or screen you go for fx705dt because the screen size is 17 inch, Boht the laptops are same as well.
Let me clearly specify the difference in the boht laptops.
The boht laptops come with AMD processor Ryzen 5 & 7 with 3550H & 3750H.
Both have 8GB Ram and it can be expandable, 512 GB SDD their or 1TB+256GB is their as per your budget or requirements you can buy it.
Pre loaded Window 10 in both the laptops, No Ms office is their.
RGB blacklight Anti-glare IPS Display in both the laptop.
NVIDIA Geforce GTX 1650 & 4 GB graphic card for editing the videos in boht laptop.
FX505DT have 120Hz refresh rate while FX705DT had 60Hz as normal.
FX505DT came with 15 inch screen display with full hd screen donation IPS and FX705DT come with 17 inch screen with full hd screen.
FX505DT have 48 Watt of battery while FX705DT have 64 Watt Of battery.
4 core are their in FX705DT & 3 Core are in FX505DT.
Comment your quires for getting clear view.
Thanks you
Vishalvs 