So someone's selling a Line 6 M5 stombox modeler ($100) and a Boss GT-3 ($150). As I'm looking into buying an effect pedal, I'm torn between which of the two to get. I know they're very different and not really comparable: the Line 6 M5 can only simulates stompboxes and it can only do one at a time whereas the GT-3 is a multi-effect pedal and can simulate amps etc too.
But my question is: which sounds better? Especially seeing as I'm interested in using it to play metal and rock music (90s rock/grunge). Which would you recommend I get? Thanks!
If I had to choose- and by had to I mean I was held at gunpoint and told I was going to buy one of those two - I would go for the Boss. Unfortunately, I can't give any pros to either of the two, because I personally don't like multi-effects processors. But I think you could have more fun with the Boss.

For what it's worth, I recommend saving your money and buying separate pedals.