This is only my opinion
The 7 bolt head is very different than the 6 bolt head in the actual design and performance. The 6 bolt head, like stated, has very large ports which can flow a great deal of air. The 7 bolt (95'+) head, has smaller intake ports creating higher velocity. There are multiple other changes in the bowl and guide area's as well. This higher velocity helps in making more power down low through the mid-range. IMO the best combo for a engine under 700-800awhp would be a 6bolt bottom end with a 2G head. You will greatly improve your drivability on the bigger turbo's with the 2G head. Anything over 700-800awhp, you would want the 1G design to maximize airflow and not have any restriction. This of course is my opinion, but there is a reason why Mitsubishi changed head design midway through production. With that said, I have a 1G head, so I am not biased. Bigger is not always better in certain situations. You will get a thousand opinions on this, but just know that both heads will make power, only the 2G will shift the powerband a bit. Good luck.
2013 DSE winner