There really is no comparison. Plaster is a low cost option but is certainly inferior to other products. Due to regulation changes plaster is not the same as it was many years ago & therefore the life expectancy is only about 7 years. It is also susceptible to discoloration and staining more than pebble finishes. Initially plaster pool interiors are about half the cost of doing a Pebble Sheen pool, however they are more expensive over the lifetime of the pool.
Pebble pools have far superior durability over plaster pools. PebbleTec has a 5 year warranty on the product, but with proper care the lifespan of the Pebble Sheen will be in excess of 15 years. Pebble sheen is a harder & more vibrant product that is more forgiving to improper maintenance. PebbleTec comes in a variety of sizes, styles, & colors so ever if you like the brightness of plaster there is a pebble sheen color that will give your new pool the same look.