I've been using the Airflo river & stream floater for my 6wt and love it. Floats really high, shoots good and has 5 year warrenty against cracks. Rio lines are supposed to be very good also. I would stay away from Scientific anglers stuff. Even the mastery series lines crack in a year. I've used several cortland lines too, and they were decent lines, but in my opinion the Airflo & Rio lines are much better.
I used to fish Scientific Angler Double Taper and Weight Forward Floating Lines. Then I tried a Wulff Floating Triangle Taper line and have become a fanatic about them. They load with one or two false casts and mend well. When I fish with people now I invariably let them take a cast or two with the line just to watch their reaction. Have yet to find someone who tried the line and didn't want to keep fishing with it the rest of the day.
I'd spend just a little more and get him a multi tip line. I know there about twice as much as a floater in the shops, but I've seen them new in the box on E-Bay for $70-$80. I switched over to them a couple of years ago and love them! :THUMBSUP