I'm certain those in the Boston area (beantown?) can recommend a good local custom cabinet maker. These can be competitive in price to any mid to high end manufacturer. I went with Crystal, which is made in Minnesota. In the price spectrum, it is considered mid-high. I am quite satisfied thus far, as I near completion.

Are you using "custom" and "semi-custom" to refer to the cabinets or the finish? Custom cabinets are specifically made to measure to exactly fit your space. Semi-custom are bought pre-made and fillers are used to make the pieces fit the space. A custom finish should use hand-applied stain with attention to evening out the variations in wood tone, and covered with sprayed pre-catalyzed lacquer. I dunno about "semi custom" - maybe everything is just sprayed, without the care regarding wood tone variations.

Link to recent discussion on plywood vs particleboard vs MDF: Here is a link that might be useful: click

Cabinets made in Ca when made legally are to be finished with water based paint and stain products. The cabinets made in South Dakota like Starmark and Showplace are oil based catalyzed varnishes which are much more durable. If you want to test it. Ask to have a sample from both places. Put acetone on the finish and wipe it off. If it is water based the finish will dissolve to some degree during the wipe. The oil based finish will look un touched. The La area store of Ca I work does not offer locally made cabinets for this reason. If you want to buy oil based floor stain or poly urethane you have to drive to San Diego county just to purchase it... The basic premise of the what the dealer told you is correct... The acetone test will tell you if you will get a inferior finish from the local company... I have heard of one company that made cabinets for a project I bid and did not get where the local cabinet maker bought oil based finish in pints to have it shipped in from out of state. You would have to mix all them together I would think it get an even finish color... The national cabinet makers use the oven and the catalyst to be able to finish their products faster. The upside is most also add an hardener to the finish that cures with the oven making the finish more resistant to light scratches and other wear and tear.. I have spoken with many people who have locally made cabinets where the area around the knobs and pulls discolors over time from the oils in the skin from being touched. The out of state finish is likely to be more durable from a reputable company in South Dakota.