Paralell WLAN/Wifi file transfer slower than sequential?

Assume I have two computers A and B which are connected (through WLAN/Wifi router) in an inhouse net.

Now I have to transfer huge file archives (> 10 GB) from A to B and other huge file archives from B to A.

I could either do this file transfers
1) in parallel (=start copying files from A to B and from B to A at the same time)
or
2) wait until file copying from A to B is finished and then start B to A.

What is faster?

I could imagine that protocol overhead and interrupts in case 1 could slow down throughput.
On the other hand I could use in case 1 unused upload capacity into the opposite direction during download.

Any recommendations for this scenario?

Peter

Safer is point 2.
It may use some RAM or pagefile to store the buffer.
Read is faster than Write.

Go to a shop deal with cable.
Ask for twisted cable where you can joint both computer, to able to see both.
Ask the staff as they will explain more in detail.