The so called "flank drive" which was a Snap-On held patent is said to round fasteners less. I believe that may be true, especially on softer fasteners, however, I have not done any studies, nor have I seen any peer reviewed studies.
Most sockets and wrenches I have bought recently have that feature.
BTW, it may not be true for Craftsman today, but I believe that Allen made many of their wrenches in the past. They have similar features, wear characteristics, etc.
For most people, their use of flare wrenches will be sporadic. If you need to do lots of work with flare wrenches, consider buying mid-line and then upgrading as your usage increases.
The use of good penetrants, and sometimes heat, may help your success as much or more than the differences in flare wrenches. If you can apply shock to the fitting that can also help. Sometimes loosening, followed by a slight tightening, helps free up the oxide particles, and keep fittings from binding so that they might fail.
One final thing, I like my flare wrenches snug. I don't mind tapping them on, if it helps me loosen a fitting. So you might take a steel fitting of the size you are interested in, and see how much play a given wrench has.