I only can give you a comparison of the '13 models as I've ridden a '13 Flagship for about 40d, and did demo the Highlife a day. The rocker nose in the Flagship is far more pronounced, rises right behind the last insert, and is - compared to the rest of the board - softish and as such, delivers great float. I'd say, the Flagship is a freeride board that should be used as that; you'll have a lot of fun with in pow, riding big open lines at speed, and on good groomers to carve and bomb, but it shouldn't be bought as all-day all mountain board.
Had a lot of fun riding the Highlife but didnít buy it since it was too similar to the Flagship on groomers. Both are comparable in many aspects: agressive, stable, predictable, fast, and stiff. In uneven terrain the Highlife may be a tiny tad less tiring, however, that's splitting hairs. It sure is also no fun in moguls as well and will need a lot of leg work there. Haven't ridden it in pow so can't comment there.
The average human has one breast and one testicle ~ Des McHale