My daughter wears Ortho-K lenses and has done since she was 9 (she is 13 now). We chose them because her eyesight was deteriorating rapidly and she was near the -5 threshold so it was then or never - if she'd had a milder prescription I wouldn't even have considered it at that age. (For context, I am -11 in both eyes and she was following a similar path to me. My younger DD, now 10, is also short-sighted but much more mildly, like their dad, and wears glasses).
They have been very successful for DD1 and appear so far to have arrested the deterioration in her eyesight. This is the big advantage of using them, along with the fact that she can, for example, see when she's swimming or play sport without worrying about breaking her glasses or losing a contact lens. I also think they are less hassle than daytime lenses and easier to wear as there is less scratchy movement when your eye is closed for sleep.
BUT they are rigid gas permeable lenses, not soft, and as such take a long time to get used to and are still fairly uncomfortable - DD1 sometimes asks if she can stop wearing them for a while but they only work if you wear them every night and you can't switch to glasses as backup. Sometimes she "forgets" to put them in and the next day she can't see. We also still have to nag her about hygiene and I can't see that improving anytime soon even though she is quite sensible and mature for her age.
It's also a very expensive commitment - five years ago it was 250 pounds upfront with no refund if she couldn't cope with the lenses, and we pay another 45 pounds every month (for which she gets a new pair every six months). This will need to continue until her eyes have stopped maturing, probably when she is about 21.
For those reasons I would say the benefits of Ortho-K outweigh the negatives only if you're very short-sighted or on that trajectory. But they're great if that's the case, and having spent a lifetime with severe myopia myself, I don't think anyone with a mild prescription really understands how debilitating and costly it is - I wear contact lenses but my "backup" glasses cost a more than a grand a pair, so please don't throw me a ball, I need prescription goggles for swimming or I wouldn't be able to find the pool (literally, forget not being able to read the signs), I feel unsafe driving in my glasses because the lenses are necessarily so small I have little peripheral vision ... if DD1 can avoid all that it will have been worth it.