MP3 and YouTube rips suck ass. I take the character and grittiness of analog sample-sources (vinyl, cassette, etc.) over low bitrates and digital artifacts any day.
Vinyl has an audible broader frequency-range than your average 128kb/s MP3 file, because the MP3 format uses a lossy data compression algorithm to squeeze a whole song into a 3MB file. This means you lose audio-frequencies vital to the feel of the sample. MP3s ie. will generally lack bottom end which makes the sample less beefy. Especially if the MP3 is a YouTube rip. Then you get a 3rd/4th generation audio file with no character to it (and lots of digital artifacts).
I sample from a CD here and there, but I try to avoid it, simply because digital formats are also too cold and the digital signal is flawless, so there is no character added like tape or vinyl does...
There's also a great tradition for vinyl in hip-hop (and other related genres). If you are new and cocky and the best producer in the whole world, then you probably don't care about hip-hop tradition and history. I do. I carry on the tradition of the legends whom I learned everything important from just by listening to their music: Marley Marl, Mark the 45 King, Buckwild, DJ Muggs, Dr. Dre, Lord Finesse, Pete Rock, DJ Shadow, etc. etc. etc.
But just to flip it 180, I will say this: do you. If you don't give a flying duck about all of the above, then sample away from sucky Youtube channels, and be lazy: get all your samples from online MP3 blogs. God forbid that you'd have to actually get hands dirty with cratedigging in a record shop...
NB: I haven't read any of the replies to OP, so sorry in advance for repetitions.