I think both are very bold pieces that make a statement, but I think the Black Multicolor is going to be a bit more versatile. But it is all about what you feel more comfortable with, and your own personal style!
It would depend some on what is in your collection. I love my mc speedys - they are the reason I fell in love in my LV. But now I am starting to really loving the seasonal items (and always regret when I do not get them!) So I am really no help!
Hmm!! That's a tough one. Both are excellent bags. MC speedy has been around for years and the price of it keeps going up. As for the pink graffiti, it will only be available for a short time. In another words, the graffiti bag is very trendy and stunning. But if you can see yourself carry this bag for years, then by all means get it. MC speedy will always be around to purchase. I get the pink graffiti speedy now so no regets later.