After delving into this topic in much detail on my build. I'd recommend looking into the fin density before you buy a core. Ideally you'd want staggered or offset dense fins that will really disrupt and then cool the charge. ETS, Process west all have proven results and there's pics to prove the fin density. Others are a bit hit and miss imo. Some of the cheaper ones like HDI and even some of the cheaper Chinese stuff for sale here in nz seem to have good dense fins which could work well also. Personally don't think the mishimoto cores are great. And the Perrin ones look awesome but aren't as dense as the ets or process west ones. Despite being soooooo pricey. Havent managed to get a pic of the cobb core fins yet, but I'd take a wild guess and say similar to Perrin.
Just stay away from the stuff that is basically straight through with no offset or staggered fins.