When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Don't have experience with stacking on either one but I would lean towards the edge comp. Which ever one you decided on make sure you run the smarty on even numbered tunes it doesn't add timing that way.
I haven't noticed any issues with my Smarty EJWA stack. I usually leave the Smarty on level 1 for fuel mileage, which is still an aggressive setting, and then add more with the EJWA as needed.