It always depends on the purpose of your use. As in the case of YouTube video making, If you want to record only your voice, it is preferred to use a unidirectional microphone, because it captures only in one direction you don't need the ambiance sound to dominate your voice (Make sure you point in the right direction towards the mic).
Otherwise, if you are a vlogger and you not only need your own voice but you also need the surrounding sound then I suggest using an omnidirectional microphone.
Even though the purpose of the lavalier microphone is to record close to the mouth. But still, there are Omnidirectional lapel mics available in the market. Those manufacturers may have their own theories for it but, I always suggest you know the mic before you buy it.
And finally, for an opinion, If you want clean and *noise-free audio, I suggest you buy a professional one. Don't expect high quality in cheap microphones.
*noise-free - the "noise" I meant is the electric hum or the white/pink noise
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