The best bark I have had was on brisket in Lockhart, Texas. Kreuz's rub is mostly salt with cracked pepper and what looked like a small amount of paprika and garlic powder. Not any sugar in there at all as far as I could discern. Smitty's bark might have been a bit better and tasted very similiar.
I have no way of knowing for sure, but I belive the secret is more in how they smoke meat than the rub itself.
Jim - Another transplanted Texan
Former KCBS CBJ
Large and Medium Big Green Eggs , Black 18.5" WSM, Blue Weber Performer - Stainless, Green Weber OTG Kettle , Brinkmann SnP Pro, and a Stainless UDS. One retired Portable Kitchen grill.
Red Thermapen, Maverick ET-732, EdgePro Apex Sharpener.
Avatar is the original 1951 Weber Kettle