Double(or tripple you would say) loops(loop on each side of your edge) is generally always best, if you do an "edge bevel" on it, you ruin the initial edge, which can be a pain down the line, if you want to adjust, or when creating your lowpoly etc. For hte lowpoly for example, if you remove the 2 supporting edges your main shape stays the same. If you collapse the edge bevel, or remove 1 of the 2 edges there, your shapes start to get messy and not as accurate to the HP.
I was actually going to write about this in someone else's thread, but didnt get around to it.
Another side benifit is, you can easily take out the edges, and then add them back in if needed. Say you change the main edge loop and some other geometry around it, and now your supporting edges are messy. Simply select the loops, remove, and added em back in using loop slice(in modo) or connect? in max.
At the end of the day there is no hard rule about it, you just need to plan ahead and see if the benifits are good for how you plan to work.