my general advice is that keep the abilities in 10 rate gap.
I would pick the 6* ,first cause he is near to 7* and secondly cause he is more balanced .

With GK's its diffucult to say,i remember i had a goaly with 17 and 18 gap in my first levels..couldnt say the difference if i dad him more balanced cause he took 5s and 6s but i believe it was cause of the rest team.Attacking mentality, took the league 25-1-0 so the GK was not so needed.The next season decided to give all the SP to phy and offe..same thing 5-6s ,same orders ,took the league not so easy although.

I have a scout ST for 2 seasons now..he has 8 and 6 gap ..he is almost every time man of the game ,he scores ,he gets 8s and 9s.

So i would definetaly choose the 6* and try to keep him balanced .
gl