That is actually dependent on what you are doing. With gigabit ethernet being full duplex, you can transfer 1Gb/s both up and down at the same time.
This would mean that if he has a single port, if he was downloading a file from the internet, he could still reach 1Gb/s. If he, however, had 1Gb up and down, he could only download at 500Mb/s and upload at 500Mb/s simultaneously.
His upload being so much lower than his download would lead to him not likely noticing any difference.