Try this for an answer.....
Mine is a 6-wt., and I use it with 6-weight line. I am sure for a beginner, you could use a 7-wt. line to "overload" it slightly, and he could get a better feel for timing/loading relationship.
Or just get the 7-wt., it all depends on what your individual needs, comfort, rivers/streams you fish, and what you need for a good all-around rod.
Since I don't know what your target species of fish are, and am unfamiliar with the conditions, I am always hesitant to make a recommendation. But here are some ideas.
If he will use it for a lot of chrome and salmon fishing, the 7 - maybe even an 8 wt. might be a better choice. For bass, I had a lot of fun with a 4-wt., but the heavier wt. rods are vastly better for casting wind-resistant bass bugs. For all-round general trout and panfish, a 5 or 6 wt. should be fine.
"You pays your money and you takes your choice!"