Hollywood undead has a more thug/jiggalo tone to there music than msi, msi generally is very not serious and not trying to be, instead of a thug life, jimmy urine sings of basically being a rizzler and msi's songs are very hedonistic and edgy but not exactly in the same way as Hollywood undead.

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there music is similar, electronic stuff but actual instruments as well, but Hollywood undead sometimes has a more metal sound whereas msi has a more rock sound to it, like punk rock.

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msi doesn't really have any " serious'' songs (other than the album pink) but Hollywood undead most definitely does.

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msi's newist album is basically 13 years old at this point and there band originally first started making music back in the 90's so there music's lyrics and such sound hella dated tbh whereas Hollywood undead doesn't sound old af but, if you wanna listen to something old like greenday msi's your go to! but if you want new, go with Hollywood undead.