Many people think that a federal crime is more serious.  That is not necessarily true.
For example, the majority of homicides are prosecuted by the state.  When murder involves a federal official or takes place on federal property, then it becomes a federal crime.

 Federal crimes are those that involve a federal law or property For example bringing drugs across the border is normally a federal crime.   More fentanyl, heroin, cocaine, and methamphetamine pass through the border at Tijuana- San Ysidro and Mexicali-Calexico than any borders in the world.  Human trafficking (alien smuggling) and bulk cash smuggling are also examples of federal crimes. 

Federal law and state law are very different.  It is important to find an attorney that has experience with the case for which you are seeking an attorney.  And sometimes cases can start out a state case and become a federal case later.  This happens frequently with drug cases and child pornography or sex trafficking.