These solve the same problem from opposite directions. An insole is something you add to a shoe you already own. An elevator shoe is a shoe built from the ground up with the lift engineered into the sole and heel. That difference in construction ends up mattering more than the height numbers do, especially for the specific question of whether anyone can tell.
How each one actually looks from the outside
Insoles keep your existing shoes exactly as they are on the outside. Nothing about the shoe’s shape, sole thickness, or proportions changes, because the lift is hidden inside. The tradeoff is that your foot is sitting higher inside a shoe that wasn’t designed for that, which can show up as a slightly different angle at the ankle or a shoe that looks a touch more snug than it used to.
Elevator shoes are designed around the extra height from the start, so the sole, heel, and toe spring are all proportioned to match. Done well, this actually looks more natural at higher lift amounts than an insole crammed into a normal shoe, because the whole shoe was built for that height rather than adjusted after the fact. Done poorly — and there’s a lot of poorly made stock in this category — the sole looks unusually thick or the proportions look slightly off to anyone who happens to look down at your feet.
Cost and commitment
Insoles are cheap and disposable. You can try a pair for $20–40, decide they’re not for you, and you’ve lost very little. Elevator shoes are a bigger commitment, usually $80–200 a pair, and you’re buying into a specific style, so building a rotation of them for different occasions costs meaningfully more than owning a few insoles you can move between shoes you already have.
Comfort over a full day
Insoles change the internal geometry of a shoe that wasn’t designed for the extra material, which is where most of the “my feet hurt by 3pm” complaints originate. Elevator shoes, when properly made, distribute that height change across the whole sole rather than concentrating it under the heel, which tends to be more comfortable for long days on your feet, though the break-in period can be longer since it’s an entirely new shoe rather than an addition to a broken-in one.
Which one actually answers “can people tell”
For height gains under an inch, insoles inside well-fitted shoes are close to undetectable. Past that, elevator shoes generally hold their shape and proportions better than a shoe with an insole stuffed into it, simply because they were engineered for it. If discretion at higher heights matters more to you than flexibility or cost, elevator shoes are the more reliable choice. If you want to test the waters cheaply, or you want to keep your existing shoe collection, insoles make more sense as the starting point.
General product information, not a substitute for a fitting from a shoe professional if you have existing foot or joint issues.