Hi Cheryl, great to see a fellow Ontarian here on Houzz!!! I am a cabinet maker and I have to say when it comes to doors/drawer fronts and applied gables I have found that with out a doubt cnc'd MDF is the way to go. For years in my own bussiness and other places I have worked I built many painted kitchens out of paint grade woods such as #2 Hard Maple, Soft Maple and even Poplar. I have built 5pc doors with Hard Maple rails and stiles with MDF center panels and every single kitchen or piece of cabinetry I have had has had issues with movement. I build all my own wood doors as I don't like the the way all cabinet doors are being made now a days (the construction is the same, but I allow the wood panels to dry 1 week before sanding, and after the assembly of the door I let the joints dry a minimum of 3 days before sanding). What happens is that sanding these doors that are assembled so quickly leads to sunken glue joints that don't show until usually the final coat of finish is applied.
Getting back to the painted doors...even an MDF center panel in a wood framed door will still shrink and expand with the changes of humidity, even small changes will cause cracking in the finish or unfinished paint lines showing thru. On a stained/lacquer'd door you don't see this because the stain is able to creep back in under the grove in the rail and style. I now use strickly 1pc MDF doors for all my painted cabinetry, although even the 1pc MDF door will shrink and expand...there are no joints or center panel movement, there for the finish stays perfect for the lifetime of the door. The best thing I like about the MDF is the actual hardness/density of it. The problem with using paint grade woods such as poplar or even soft maple is that the wood its self is quite soft, once finished and in someone's home...if a dent is created it will usually be a very sharp dent/crease there for causing a fracture in the lacquer/paint and will start a chipping of the finish. MDF is actually harder than Hard Maple, and greatly reduces the chance of these styles of dent...although its possible to dent, it takes much more force to actually fracture the fibres of the substraight.
Everyone has there own opinions but I am a firm believer that with the right finishes (I use the very best pigmented primers and pigmented lacquer's I can buy that are made specifically for MDF) MDF doors will last a life time in even the most abused homes with no warantee issues in the future. 99% of my bussiness is by word of mouth, and even one warantee issue is not only a cost and inconvience to my bussiness but a potential lost future customer!