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I have both and the fuzzy cleans better, the smooth just seems like it moves the dirt around and leaves smudge lines. Fuzzy makes my screen crystal clear and smudgeless
 
i use those yellow microfiber cloths from Costco and the seem to be ok. I guess their the fuzzy ones.
 
i use both and both work just as well as each other

if u get lint or doesn't clean well, just fog it up with ur breath and wipe again. good as new!

should have added a poll lol
 
I have both.

For my first gen iPod touch, I used a blue and yellow microfiber cloth I got from Wal-Mart that is smooth.

For my current iPhone 4, I use a green microfiber towel cloth from Target that is fuzzy.

From my experience, I like the fuzzy ones better. It wipes away the fingerprint like a sponge. Only weakness is it could leave lint sometimes from the tiny threads. But far less streaks. A smooth one just smudges the fingerprints and needs to get washed more often because of it. Leaves streaks.
 
I prefer slightly fuzzy as I find they remove the general nastiness a bit better (oils, etc.). The smooth cloths that comes with most cases work well polishing but otherwise I find they just move oils around. That said, I'd only use the fuzzy ones on a screen with a protector, I find they trap a lot of debris which has in the past created a couple of small scratches.
 
Fuzzy ones are better for cleaning since bits and pieces of dirt/gunk get trapped in the cloth. Only downside is that, periodically, you need to launder them in order to get all that dirt/gunk out or there is a chance that those little particles will scratch your phone.

Smooth cloths don't do so well for cleaning however they are good for "light" cleaning of your phone, i.e. fingerprints/dust/etc. As far as oil goes, like others have commented already, the smooth ones will just kind of move them around on your screen and not really clean it.

Personally, I use both. Using the smooth one for daily cleaning. I use the cloth from that came with my 3G for that. And an auto microfiber cloth (maybe once a week) to do a little more thorough cleaning.
 
buy a fuzzy one, but not a cheap one you get from costco, etc

those tend to leave fibers behind and really suck after you wash them a few times

the best microfibers I have used are

1) Mother's Ultrasoft Microfiber towel
2) Meguiar's supreme shine Microfiber towel

you don't need 20 like from costco, just a few quality ones and take care of them
 
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