I would think the chances of post injection pain are much higher with test, especially at 300mg/ml... deca is very rarely painful, if the deca injection site gave u pain u either nicked something going in (bruised the area) or the deca was made with too much alcohol, which is the cause of most pip
I'm currently rotating 6 injection sites (quads, glutes, delts), injecting 1ml test e (300mg)/1ml deca (300mg) eod and very seldom have any discomfort at all