Well, foreknowledge of how to deal with virus-created zombie mutants doesn't necessarily help him against Walter Sullivan and the Ghosts, or against the whole surreality of being trapped in his own room / alternate reality. If anything, it would make him overly foolhardy, and cause him to assume that the same things work. Survival in a Silent Hill environment is knowing how to escape from demonic creatures while armed only with a golf club.
That said, SH4-->ResEvil works better, in my opinion, unless the purpose is to see him make stupid mistakes by assuming the conditions caused by Umbrella. Minimalist survival tactics (SH4 style) versus an environment filled with resources (Raccoon City) means a greater advantage (a new type of uber fic?). But that wouldn't really be interesting enough for me to look into such a crossover.
If, on the other hand, Silent Hill follows him into Raccoon City and mixes with the chaos created by the virus ...
