If I had to sum up the ThieAudio Legacy 5 in a few words for potential buyers, I would say that if you are looking for an energetic, clear treble response, look elsewhere. Just about everyone else will find these fantastic, though, especially for the money. For context, the FiiO FH7 comes with a similar 1 dynamic driver + 4 balanced armature driver setup and costs nearly twice as much. I can't tell you if it is worth twice as much, though, since this is only the second IEM I have reviewed, and the first to get a proper frequency response measurement. But I am now set up to do more, so for now, my qualitative experience with the ThieAudio L5 complemented by the quantitative frequency response will have to do.
I admittedly was not sure what to expect going in with a 5-driver setup, especially for $250, which is where things can go wrong very quickly with poor tuning, but ThieAudio proved my fears were unfounded. I now also have a better appreciation for why the upstart brand secured a lot of fans and goodwill in the ~2 years since its inception, so much so that there are people happily shelling out $600+ for other IEMs from the brand. The Legacy 5 ended up benefiting from these higher-end offerings, with a similar base driver setup as well as the tuning to go with it. The unique hand-painted resin face plates also make for a neat touch you would otherwise not get in this price range, especially once you realize that each piece is different from another and can take up to a day to make.
There is a lot to gain here coming from the Ikko OH10, be it with the much more palatable fit and comfort courtesy the rounded shape and lighter weight, better stock cable design and geometry, or even remarkably consistent bass and midrange response. As mentioned before, the trade-off is in the highs, but for $50 more, I would personally happily get the ThieAudio L5 over the Ikko OH10. There is good sound isolation courtesy the foam tips, and the silicone set is really good, too. It's not a copper and titanium weapon you can fling at others, but, rather, a glistening piece of an audio device that looks nice and wears even better.