Actually, 1688 and https://t.co/b3VsFiIH4c are both owned by Alibaba Group.
The main difference is that 1688 is designed for the Chinese domestic market, while https://t.co/b3VsFiIH4c focuses on international buyers.
You can often find cheaper prices on 1688, but most sellers mainly serve Chinese customers, so international shipping, payment and communication can be more complicated.
So neither is necessarily better. It depends on what you're buying and whether you can handle the logistics.