Edit:sorry i just noticed u meant fhe vs oh10. Not fh3 vs oh10. So sorry
I own both of them, and my thoughts are:
Both very bassy.
Both have good instruments separation.
But;
Oh10 is more bassy.Fh3 bass is like being hit with foam baseball bat. Oh10 bass is like being smothered in thick blanket.
Fh3 is abit more forward. Satisfying when it comes to vocal, but on a busy tracks, it can be abit overwhelming. Like being in a concert, held in a subway train.
Oh10, due to having v shaped sound signature, the midrange suffer, and the vocal is more recessed. But instead of feeling āveiledā, itās more like being in a concert,held in a large hall. And the vocalist decide to stand way back without using microphone.
Vocal is less forward, but in return u get wider soundstage, and instruments are more prominent. The placement of each instrument is very clear. Very airy. It is a weakness /flaw, but a flaw i personally much enjoyed.
Fh3 is more fatiguing over long listening session.
Oh10 is more enjoyable with rock music due to higher treble. Guitar distortion especially sounds nice.
Both fit well, but i have trouble more with oh10 due to itās weight. It nearly twice heavier than fh3, and the effect is obvious. Every 30,40 minutes, i need to remove the iem, take a 10 seconds rest before putting it back in.the weight has significant effect. Your mileage might varies.