Do you prefer to use the Monochrome Pea Soup effect? or the Black and white filter? Do you prefer the slighty stretched 'yet a smidge blurry' default screen size? or do you prefer the additional Game Boy Boarder with the pixel perfect sharp resolution with the shnazzy depth-ish Game Boy 3D effect? 
I use the Default Larger screen size with the Monochrome Pea Soup filter....It totay takes me back to playing Super Mario Land on my GameBoy! And while it retains a bit of that ghosting effect which is really cool, it's nowhere near as ghosty as the original GB was which is a good thing hehe.
Also, as much as I love the GB Boarder, along with the 3D effect it gives and the sharp/crisp resolution that goes along with it....It's the screen size that is twice as small as the original GB screen that bums me out....WTF Nintendo! And if you use the default screen size it's a bit larger than the original GB screen size, while looking soft and giving it a less impressive and blurrier look. Either way you can't win. 
And playing traditional GB games with the Black & White filter just doesn't seem right for some reason....Because it was never like that in the first place.

I do like the pea soup green better than having the games in black and white. It just looks so classic and gives me a warm fuzzy feeling.