DiFillipo AND Pacemaker are quite good brands (2 of the best out there next to a couple of others).
Is your 2 and a half system a twin or single? If it's a single, i'd be worrying about getting a bigger exhaust first before extractors. If it's a twin, i'd go either brand mate. They are both quality. I'd personally go Pacemaker, but i have heard really good things about DiFillipo.
Up to you really! Whatever is cheaper i guess because i would hold them as both equal to each other in quality.