After reading many posts concerning this topic, I've come to notice something...
Any time you read, "MG will work," or "WalMart nutes work great," it's usually posted by someone who has ACTUALLY used said nutrients.
Any time you read, "MG sucks for MJ," or "Cheap nutes kill cannabis," it's usually posted by someone who read it in a post by someone else, who read it in a post by someone else, who read it in a post by someone who didn't know what the f*ck they were doing and overfertilized their plant(s).
Yes, plant-specific nutrients may be more user-friendly but if you know what you're doing (2nd grade math anyone?), you can get ridiculously close to the same quantity each of N, P, and K per feeding from department and hardware store nutes as you can from Super-Organic-Suckyourwalletdry-BoostieMcBloomandgrow.