The difference between a timber frame and a post and beam structure is the way the individual parts are connected: Timber frames utilize wood joinery and rarely use steel parts; whereas post and beam structures are connected with metal fasteners and connectors.
Benefits of post and beam type construction: Reduced skilled labor costs.
Disadvantages of post and beam type construction: Moisture can condense on steel surfaces causing the steel to rust and the surrounding wood to decay. Depending on the complexity of the metal plates, can be more expensive than traditional timber framing. Dissimilar materials (metal and wood) tend to work lose over time.
Benefits of timber frame construction: Usually (but not always) more attractive, elegant, and expensive. Traditional wood-to-wood joinery, if kept dry, can endure for centuries. Finally, traditional wood joinery is somewhat elastic–in other words, it can deflect and give a little under loads. This is one reason that certain examples of Japanese architecture have survived for over a thousand years–despite the destructive earthquakes that occur several times each century.
Disadvantages of timber frame construction: Higher cost of skilled labor to design and fabricate traditional joinery. Some increase in timber cost when timber sizes are increased during engineering to accommodate joinery.