It depends on where you live, who you are trying to impress, and your chances for vandalism.
In the south, gunite pools are cheaper than vinyl pools, while in the north, they are more expensive. Gunite is a form of concrete that is sprayed into a hole in the ground in order to make a pool shell. A finish, like plaster, tile, or glue and stones is then spread over it to make the shell waterproof. In the south, this is a pretty simple job, with a minimal amount of steel wire reinforcing in the concrete. In the north, we have to keep the pool from cracking due to ice pressure. That requires a lot more steel, concrete, and expertise.
Vinyl linered pools do not crack from ice pressure; there is enough “give” in the walls and liner to just flex slightly with the pressure. So vinyl linered pools are the same price wherever you live. Linered pools can be cut, causing a leak. Now that does not happen very often in normal residential use – maybe once every ten or twenty years. And, it can be permanently repaired with a chemical weld in three minutes, for around five dollars. In a hotel, health club, or city pool, however, vandalism is a much more likely threat. In that case, the gunite has a big advantage.
Gunite pools do offer you the option of infinite customization. There are no specific sizes; just dig a hole and spray in the gunite! So you can be the only person in the world with your specific pool. Free form and kidney shapes are actually easier than rectangles, because you actually can not tell if they are off by a few inches without a blue print – but anyone can tell if a straight line is crooked.
Vinyl linered pools are available in hundreds of shapes and sizes now, so that you can still get a kidney or free form shape. It just requires more precision on the part of the builder, because the liner won’t fit right unless the walls were built right.
Gunite offers you a wide variety of interior finishes: any color plaster, rocks, tiles, paint, etc. (hint: never paint). Vinyl now offers the same selection; except the vinyl will be printed with photographs of tile or rocks instead of the real thing. So an inexpensive vinyl pool does look cheaper than a gunite pool, but a nice vinyl pool can look just like a gunite pool.
Construction techniques do vary. Generally (though obviously not always) gunite pools are built by general contractors who use subcontractors for every part: excavation, steel reinforcing, gunite spray, plumbing, electrical, plaster, tile work, decking. If you leave three to seven days between each trade so that they do not develop wasted time if one is delayed, it can take a month to complete your pool. Vinyl companies will generally use the same crew to do everything except possibly the electrical and the deck. That means installation in a week or so. In the long run, I would call that a difference, not necessarily a better or worse. Once your pool is built, you’ll forget about how long it took.
Maintenance on the two types is very different. Not counting holes in the liner (as we discussed above), vinyl liners don’t require any special maintenance until the liner finally dies. Figure 16 to 25 years with chlorine or bromine chemistry, or maybe 20 to 30 years in a PHMB (like Baquacil) environment. Then, you replace the liner for maybe $1800 to $2500 or so.
Most finishes on gunite pools, particularly plaster, are chemically “alive”. They are affected by water chemistry and they also affect water chemistry. Like a carpet, very light colors and very dark colors discolor easily. They can become pitted or scaling, causing good places for algae to grow, or even cut your feet. You can avoid or at least dramatically reduce this by taking good care of your pool and its water.
The repair for this is an acid bath, in which the top layer of plaster is etched off – like compounding a car finish. That’s maybe $600 to $1000. And, like compounding a car, you’re only going to get away with this two or three times, and then you’ll need to re-plaster to the tune of maybe $1500 to $2500 or so. How often do you acid wash? It depends on how well you take care of your pool, and how much the stains bother you. Average, maybe about ten years. If you have to do it in two years (it is possible) that would probably convince you to take better care of it in the future!
So what do I think? For commercial use, go gunite. For residential use, go with a really nice, expensive gunite with beautiful landscaping, a built-in spa, waterfall, etc. In other words, really high end. In that case, you can also afford the maintenance – and hiring someone to do it for you. If you are more of a do-it-yourselfer, go with the lower-maintenance vinyl linered pool. But try to upgrade to a cool shape. We’ll talk more about why later in the next section.