Kind of depends on what he's using it for, but if it is a conventional saw, I have and like my Makita. But mostly I use my 18v DeWalt. If I were buying a battery operated saw again, it would be a Bosch, but that brand choice is true for most replacement tools. The potability of the DC circ saw is a gigantic plus for me. Get one with a 20v battery, the new type, unless he already has some tools with another type, brand or voltage batteries. The advantage of the 7.5 circ saw is raw power and half an inch deeper cut. But I love working with the lighter and quite powerful 6.5 inch saw. I often break down sheet goods while still on the truck and for that, the battery operated saw is a delight. The blade is very narrow kerf, and it is really easy to keep straight on a simple straight edge jig.
The more I do, the less I accomplish.