Solar lights make the most sense for homes with a path, a porch, or a patch of garden that nobody wants to run a cable out to, a rented place where drilling into brick for wiring is out of the question, or a backyard that only needs a soft glow for a few hours after dinner. If you want real brightness to cook or read by, or you live somewhere with long gray winters and short days, think twice, because solar is only as good as the sun it gets, and a shaded yard under a big oak is going to leave you disappointed by October.
When you're picking these up in a shop or unboxing them the day they arrive, check the panel itself before anything else, since a bigger panel usually means a steadier light rather than the dim flicker you get from the tiny ones. Look at how the stake goes into the ground too, because the flimsy plastic ones snap the first time you hit a root or a patch of clay. Check the switch is easy to reach without crouching down, since you'll be doing it more than you think in the first week while you figure out placement. Where they go matters as much as the light itself, they clash with anything that already has a strong design statement going on, a nicely lit modern facade with clean architectural lighting does not need a string of little solar globes competing with it, and they look wrong lining a formal, symmetrical path where you want precision rather than a soft scatter. They also don't belong anywhere near bright security lighting or a porch light on a dusk sensor, because the solar ones will just vanish into that glare and you've wasted the money. Morning is actually the test that matters more than evening, since that's when the panels are charging, so a spot that looks shady and pleasant at seven in the evening might be getting almost no sun at nine in the morning, and that's the number that counts.
Be honest about the limits too. These are not a substitute for real outdoor lighting if you need to see your steps clearly at night, or if you're lighting a space for cooking or entertaining after dark, the output just isn't there and a cloudy stretch of days will leave you with almost nothing by evening. They're also not built for permanence, most won't survive many winters outside before the battery gives out or the casing cracks, so treat them as something you'll replace every couple of seasons rather than a fixture you install once and forget.
Next time you're looking at one, check the panel size first, everything else about how well it performs follows from that.