It's a matter of where you want to render it really or what engine you're going to use it show your stuff, it's basically an issue of Tangents (the math which tells how the Normal Map will be processed and shown) so you will avoid seeing any nasty seams.
A quick idea on why people do the splitting thing.
As for the splitting itself, anything that looks like it has a harsh angle, 75-90 will need to be cut since harsh bends will create a gradient in your normal map. Basically, anything that is harsh like a box edge will need a nice cut to put it simply.
That's the most common way to do it, the other way is to put up some support loops (Google it to get an idea of what they look like) so that the Normal map has more vertices on which to interpolate the data and tighten it.
Next, you need to split your Smoothing from your UV's, I know that TurboTools (free script) allows you to do this, not sure if TexTools allows since last time I used it, it did the opposite and the site it down for me currently, so check this one out: http://www.matthewlichy.com/turboTools.html
After all that is done, you need to specify a cage, usually, it's something as simple as putting Cage modifier in Max on your Low-Poly, exporting it as a Mesh, adding a Push modifier and moving around the points, collapsing everything, and importing it back as a cage (please look up Cage and how to how export/import in Max and how to change the cage).
After ALL that, you can export your High Poly and Low Poly as an OBJ to Xnormal or use SBM, which is the best way to go about it, since it's respect stuff like the tangents, smoothing groups and UV's much more correctly then OBJ (which can sometimes break if Max doesn't like something).
Take a look at the PC wiki for more information about this.
Also, don't be afraid to put in a few extra UV cuts and here and there if it's required to make your life easier.