Very astute of you to ask that question. The answer, IME, is a resounding YES, it does matter ... following are some excerpts from some of my previous posts on the subject:
~ First a bit of philosophy: The holy grail of cabinet making is "SQUARE".
Making a _perfectly square_ cabinet insures that all doors and drawer fronts will fit and be easy to install, and that the cabinets themselves, even when hung on a wall that is not plumb, will be easier to shim to that wall, and that those doors and drawers will always work because the cabinets will remain square even if the wall moves, which all walls will do.
The easiest way to achieve "square" in your cabinet making is to _batch cut_ all the component parts.
IOW, set the table saw fence ONE TIME ONLY, and cut ALL the component pieces that are going to be 1 1/2" wide at that time BEFORE moving the table saw fence to another setting; Set the table saw fence to 30", and cut ALL the component parts for ALL cabinets that are going to be 30" long, BEFORE you move the table saw fence to another setting.
Repeat as often as necessary to batch cut all your cabinet parts, rails, stiles, end panels, floors (which includes the top in industry parlance since they are the same size), and backs.
The same goes for router setups for dadoes and grooves.
Back in the 60's I got a good start on both appreciating, and learning how, to build cabinets by working with a cabinetmaker in England whose family had been in business just a few hundred years. :)
When it came to building kitchen cabinets with traditional face frame cabinetry I dissected what the cabinet factory industry was doing, figuring that a mix of my two learning experiences would allow me to build a superior cabinet, in an efficient manner, and in a one man shop.
This is the method I have adopted in my business and it works quite well for me. Others may have their own methods, thus the plethora of books.
Indeed, I've read them all, take a little from here and there, and depart from them in various ways. One way is as you have noted, building the face frame first ... this is basically what many cabinet factories do, because, when you analyze the fabrication process, it is both more efficient, less labor intensive than trying fit a face frame to a carcase, and also guarantees a square product.
I'll take two birds for that one shot any day. :)
The idea is to take the time to make the face frames FIRST, with meticulous attention to making the face frames as perfectly square as possible (easily achieved with _batch cut parts_ ), AND then assemble the casework on top of that square face frame, basically insuring a square cabinet.
Route the necessary dadoes into the backside of the face frame to accept the ends of the casework.
Route the necessary dadoes/groove into the _end panels_ of the cabinet case.
Assemble the face frames using pocket hole screw joinery.
Once your face frames are completely assembled, with due attention to them being square:
Lay the face frame, dadoes up, on a flat surface and assemble, and glue and/or nail the previously dadoed case work plywood component ON TOP OF THE ALREADY ASSEMBLED, SQUARE FACE FRAME.
Doing it this way, and only this way, absolutely insures that you have the squarest possible cabinets; cabinets that will not only attach to each other easily for a cabinet "run", but cabinets in which the doors and drawers will always work until the house is torn down ... something that can only be achieved, with any assurance, with properly made, _shop built_ cabinetry!
Let me know if you have any questions.