The speaker on my iPhone 4S stopped working, is it best to send into apple for repair or have Verizon replace with a refurb phone?

Apple will replace it if it is defective. They do not repair iphones.

Apple handles all repairs/replacements on the Iphone no matter where you bought ti or what carrier it uses - Verizon doesnt get involved in Iphone repairs or replacements

Verizon does indeed handle this as well as Apple.

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If you have reviewed those articles and still need service for your iPhone, you can contact your carrier(except AT&T and Virgin Mobile) or Apple. "

http://support.apple.com/kb/index?page=servicefaq&geo=United_States&product=ipho ne

you are right - it looks like for ATT phones only Apple provides hardware support