Here you will find information to become an informed SUP owner.
SUPs today are made from EPS foam. It comes in 1 lb, 1.5 lb, and 2 lb density. Not to be confused with polyurethane foam (Clark Foam). Polyurethane foam is not used in SUP construction anymore. It is way too heavy.
1 lb) This is the foam most often found in Asian built boards, and most raceboards, regardless of origin. This foam is so light and tender, a shaper must be extra careful handling the blank. It will dent from your finger pressure! Yes folks, this is 100% true.
When using this foam, the board skin must be engineered extra durable. This is why you see so much use of Bamboo skinning in Asian built boards.
The advantage of 1 lb foam is the blank weighs less and the foam is much cheaper. On a 150 liter board, the blank weight is 2.6 lbs less than a board built from 1.5 lb foam. But, in the real world it does not get you a lighter board in most cases. That 2.6 lb weight savings gets used up engineering a tougher skin. You need a tough skin weighing anywhere from 5 to 8 lbs more. The net is often a heavier board.
The exception is skinning the whole board in carbon.
Note: PVC skinning (a.k.a Divinycell) was used a lot to toughen the skins. Unfortunately it makes the board surf terrible compared to other constructions. It gives that stiff, corky feel, Surftechs were famous for. Today, even Surftech is moving away from this construction. It may be fine for some SUP applications, but if you actually surf your board, you don't want the whole board wrapped in it. It is more common today to see just small patches of PVC foam used strategically to spot reinforce.
Most of these extras added to engineer the skin tougher for 1 lb foam use, automatically require the use of vacuum bagging.
1.5 lb) This is the most popular foam density for US built custom shapes. It is much more durable than 1 lb. This allows traditional surfboard factories in the US, to shape and glass boards the way it has always been done. Quick, simple, and economical at US labor rates. The weight and durability can beat boards made from 1 lb foam, but not always. More important though, is boards built this way feel and surf better. For surfers, this is first and foremost, the most important point.
2 lb) This foam is mostly used for prone surfboards. It adds too much weight for use in a SUP.
Non Technical Lingo - EPS is the styrofoam used in packaging and your coffee cup. When EPS is used, the board is always epoxy.
E glass) This is the most common glass used today. It is also the lowest cost glass. 90% of SUPs are built using this.
S glass) This is stronger than E glass and cost 50% more. You find it used when customers demand the best and are willing to pay more to get it. I think it is more ding resistant.
Carbon) This is 5 to 10 times the cost of E or S glass glass, depending on the carbon weight. Lighter carbon cost more than heavier grades!
Epoxy is the resin used in all SUPs today.
When you hear the term "glass board" that is an old term used by surfers to describe a board built with a polyurethane core and polyester resin. Technically, all boards are glass boards (made from E glass or S glass). Few people use the term today because it means nothing and is often misunderstood.
Epoxy SUPs are generally more durable than the surfboards of the past. They don't get spider cracks like surfboards of old, made with polyester resin. They take abuse quite well, within reason.
They are not plastic kayaks, so they should be treated with respect. With a little common sense, and reasonable care, they will last a lifetime.
Should you happen to ding an epoxy board, it should be removed from the water immediately. With EPS foam cores, water intrusion is likely. The rate of water absorption varies with the grade and manufacturer of EPS, but any EPS could suck water. You sometimes hear claims that certain epoxy boards don't absorb water, but take it with a grain of salt. Marketing people love to BS the public. In an emergency, 5 minute epoxy from the hardware store can be used to seal small dings. For anything larger, seek professional repair.
Very few boards are actually molded anymore. People often refer to Asian built boards as molded, or pop-outs, when in fact, that is no longer true. The techniques used in Asia, are not that different from the US, in many cases.
Vacuum bagging is not the norm for the surf industry.
It is standard in the windsurf industry, and has been for 30 years. Why has the surf industry avoided vacuum bagging like the plague, for the last 30 years? Because it adds a lot of cost and surfers can be cheap. They won't pay over $400 for a board.
Why are windsurfers willing to pay for vacuum bagged boards? Because their boards fell apart when they were not vacuum bagged. The loads from the sail, the loads on the fin going 30 mph, the high jumps, all would destroy a windsurfer if built cheap like a surfboard.
Keep it simple stupid. That is how you should view everything written above. I could go on and on about the technical side of things, but then you'd probably get bored by my ranting.