Playground sound is probably much safer. It's also a great deal less expensive. Calcium sands apparently don't dissolve well when swallowed, and the particle sizes are larger, so there's a greater risk of impaction from ingestion. As for neutralizing digestion, probably not, as we regularly dust our crickets with digestable calcium anyhow. Also, since they barely dissolve, very little calcium is actually liberated to interfere with digestion.
I realize some people prefer to completely (or nearly completely) eliminate the risk of impactions, and use paper towels or tiles....I think the geckos likely prefer a more natural substrate, one they can dig in if they like, so I use playground sand. Most people who use plain sand never have a problem. Small amounts of sand pass through the intestinal tract without issue. Use a feeding bowl to minimize sand-swallowing, particularly with mealworms and other low-slung crawlies.
It's very cheap, about $2.50 for a 30 pound bag. You can spot-clean it with a sifter, and replace it regularly without a wince. If it gets wet, it just dries out again, rather than growing mold.
I don't personally approve of the folks who crowd geckos into very small enclosures with just the bare minimum of necessities. Just because they will tolerate this and breed does not make it ideal for them psychologically, they are very hardy animals.
Mine are on sand, with a dry hide area, a humid hide, and when appropriate, a laying box is put in. They also have a dish for water and for food, and branches to climb on. It is a sweater box, which I consider to be a minimum space for 3 geckos, but it is not just a box with newspaper and a tupperware container full of vermiculite, and nothing else.