The EEFC is a good place to find vegan packaged food, cleaning products, cosmetics and other stuff that Giant Eagle won't carry.
It's neither more expensive nor cheaper than Whole Foods, I've found. Some items are cheaper, some are more expensive. Some you can only find here, some you can only find at Whole Foods. I do try to support the co-op as much as I can though, since it's a local deal.
What's also nice here is you can order things by the case - usually even things they don't normally stock - and save some money that way. I often buy soymilk by the case here. It's never taken more than 5 days for an order to arrive, for me at least.
The bulk section is also good here - especially the huge selection of spices. You'll also find pastas, rices, nuts, dry beans, nutritional yeast, different kinds of flour, sugar, peanut/cashew/almond butters, tahini, coffee, oils, soy sauce, maple syrup, dried fruits, raisins, oats, some premade foodstuffs like soup mix, granola, etc. and even bulk dish soap and liquid soap. You can bring your own reusable container - for things like dish soap and such - and have them tare the weight of the container before you fill it up. The bulk section is one area where the co-op is clearly superior to Whole Foods.