Pros - More efficient use of space since double
           width stiles can be avoided. 
         - Many wood material options. Most of the
           wood will be treated and handled here
           in the US reducing issues like warping

         - More "design driven" with no limitation on
           cabinet sizes.  Gives homeowner more
           control over what they want for the
           finished product
         - Almost an endless choice of door styles,
           color finishes, moldings, accessories &
           hardware           
         - Finished product can be nearly flawless
           if you are using a very experienced
           cabinet maker
          
Cons - Cost, cost, and....cost!!! A true custom
           design and installed kitchen for example
           is extremely expensive, costing $350+
           per linear foot installed.
         - Time consuming.  Always the possibility 
           of lead time on special wood and finish
           materials. Installation will also take 
           longer with custom cabinets.  

Pros - Price.  Typical price for RTA cabinets is
           $100-150 per linear foot.
         - Ease of installation.  Typical RTA
           cabinets are pre-fabricated with cam-lock
           style construction for easy pre-assembly
           of the cabinet carcass and door/frame
           prior to installation
         - Less time consuming; due to the 
           cabinets already being pre-fab
           the are already "ready-to-
           assemble(RTA)
Cons - Lower grade/hazardous materials
           such as formaldehyde are used
         - Inferior training of mfg workforce leads
           to inconsistencies in final product
         - Lower grade hardware such as side-
           mounted drawer glides & specifications
           such as 1/2" Grade C plywood are used
         - Looser mfg tolerances used          
         - Mass produced and stored in
           warehouses so sizes, styles, and
           color choices are very limited 
         - Sub-standard environment can lead
           to issues such as warping                   

Even though our cabinets our mass produced overseas, we have incorporated many of the US custom cabinet specifications into our cabinet designs and have required the manufacturer to follow them.
Thus we have produced 

cabinets that are extremely durable high in quality:  

Heavy-duty, anti-slam, soft-close, under mounted drawer glides - More stable and hold much more weight than standard drawer glides. Soon we will incorporate new anti-slam door hinges for all of our cabinets!