The alloy manifolds look better but honestly why I picked one up was because of the integrated PI and meth bungs on the BMP unit. I really hate using spacers, more chances to leak, and I wanted the PI to be positioned properly into the port. All the extra bungs are great for sensors like the AEM, Hobbs, vacuum lines or whatever. Design wise even the OEM style does improve on the plastic some, there's no bump going to cyl 6 for starters. Heat concerns can be mitigated by a phenolic spacer though I don't really think it's necessary, and weight wise the OEM style is lighter than most of the forward facing, which was important to me because added weight is a PITA.