Longer is better?

OK  not too short and not too long then. Good quality a must. 

"Ok literally had a retailer tell me I should want a longer digital cable (USB to be specific) vs a shorter one."

@rjduncan - In the case of a USB cable, your retailer is misinformed.  He is likely referring to the belief by some experts that a length of at least 1.5M is optimal for digital S/PDIF cables, and mistakenly applying that to USB cables.  Most successful salespeople are good on the people side of things but not all of them are as strong technically.  Just being ignorant of technical information does not necessarily make the retailer a "sleezball salesman", even considering all of his flamboyant hyperbole. 

I have told my wife for years that size doesn’t matter except for stereo equipment, cars and boats.  There only logical conclusion is someone selling cable by the foot is trying to get you to buy the longest ones.  Say good day to you sir and/or madam and purchase your cables elsewhere.  

There is a little bit of proof to that , a 1.5 m in a high quality cable sounds slightly 

better why via the shielding  slightly better filtering , Audience ,has show ,

and my uncle being a digital engineer had measured on testing scopes and found msybe 1-2% better if you have gear and loudspeakers ultra resolving then  maybe yes to longer ,if not 1 meter minimum.

@rjduncan 

Now there’s a bad salesman for you. Bad mouthing my equipment is definitely a way to keep me from going back to his shop.  But he was sort of right about one thing, you might have issues with a to short cable. At least a meter, 1.5 meter is supposed to be best. Having said that, I have two digital cables.  One is 1/2 meter and the other is one meter and I can’t tell the difference between the two.