What is worse

[Bored Of Education]

Musicians trying to be actors or actors trying to be musicians?

I would go for the former as any idiot can make a half-decent stab at being in an average band whereas it is very easy to be a terrible terrible actor.

[WOM]

What is worse

I agree. I think that was proved quite often in the '80s, when music videos often had a storyline involving a bit of dialogue or 'acting'.
See Springsteen's "I'm On Fire" for an example of egregious musician-acting.
Having said that, Levon Helm was quite good as the grizzled, blind prospector in The Three Burials of Melquiades Estrada. And then there's Sting...

[G-Man]

What is worse

Then you have Jennifer Lopez, whose first ambition was in the direction of music, but who became a movie star before finding supercelebrity status through her regrettable musical endeavours.

I'd argue that Lopez is not a bad actress. It would have been preferable if the woman who considers herself firstly a singer had rather stuck to acting.

[Beatle Simon]

What is worse

I remember reading in Smash Hits, around 1986-ish, that there were rumours of a re-make of Oliver Twist with Madonna as the artful dodger, Tina Turner as Fagin and Mick Jagger as Bill Sykes. Perhaps Bowie and Sting were busy.....