To make this easy for everyone, the size of Vigoro’s and PVP’s perlite is nearly identical. The only difference is in cost. If you’re already going to Home Depot, go ahead and get a bag of Vigoro. If you’re busy, buy a bag of PVP’s perlite off of Amazon.
Vigoro perlite bag versus PVP perlite bag. PVP is 4 cubic feet and Vigoro is 2 cubic feet. 
Vigoro’s perlite 
PVP’s perlite 
Honestly… 
The perlite from both brands are nearly identical… 
Don’t forget your mask and gardening gloves
Perlite Size
Both Vigoro and PVP branded perlite are nearly identical. Vigoro’s only looks larger at first glance because more settling seemed to occur in PVP’s bags. Once you pour them out there’s nothing differentiating them.
Cost
Vigoro’s 2 cubic foot bags sell for $17 before tax at Home Depot.
PVP’s 4 cubic foot bags self for $35 on Amazon with free shipping.
Meaning that Vigoro costs a whopping dollar less for 4 cubic feet than PVP.
Keep your eye out for any discounts and bulk deals though… that might change the equation for you.
Safety Reminder
Remember to wear your gardening gloves and a mask while emptying out your perlite. While perlite is safe in a general sense, perlite dust is an irritant and long term exposure can be hazardous to your lungs. This is true of many fine dusts… sawdust… coal dust… heck did you know sugar dust is explosive?
Anyways, once you pour it out and mix it into your soil you’re done and won’t need any safety precautions.
Ultimately
The only difference for you, at the current price, is convenience. Do you want to go pick it up from Home Depot or do you want it shipped right to your door?
Your call…