The problem with either of those setups is you don't get the flexibility of being able to use the same portable, quiet and power-efficient laptop for both work on the go and for gaming at home, so you never have to worry about keeping things in sync between multiple machines (which is easy enough if you just need files, but often impossible if you also want to sync arbitrary settings for frequently used applications).

For many people like myself, the TB3 laptop + GPU dock combo is worth a lot more than the sum of its parts.