Yes, state laws should take precedent. Federal laws are essentially only there as back up laws in case a state has no particular law in their books to cover a particular act or situation. For instance, federal law prohibits the sell of marijuana, and this is the de-facto law for many states who have yet to make a decisive law regarding such a practice.
In the end, state laws should take precedence, but they should follow the federal laws to some extent and not go completely against them. For instance, legalizing marijuana goes against federal laws, but the drug is not considered a dangerous drug as opposed to heroin or cocaine. In this case, it is ok. When the state laws goes completely against the federal government in some form, like military power against the government, then the federal laws should be involved.
Federal laws should take precedence over state laws, because otherwise, we are not a union. Whether we should be a union is a matter for debate, but since we are, we all have to have the same federal laws. Where the law is passed federally is constitutional, it has to control so that we have uniformity in government.
I do not believe either should take precedence. I think the mere fact that laws between states and laws between states and the federal government clash is a huge problem. These clashes affect the citizens of this country in very unfair ways and cause problems that sometimes can not be addressed. We shouldn't have to assume one takes precedence, it shouldn't happen.