The main difference between an attorney specializing in transactional law and those specializing in litigation is the type of legal problems they are likely to encounter. Transactional attorneys deal with contracts, real-estate transactions, business formations, intellectual property issues, and other matters. Litigation attorneys specialize in disputes involving corporations or partnerships, trusts and estates as well as insurance claims and personal injury cases.
Both types of attorney require different knowledge and skills for each case. You might consider hiring a transactional or litigation attorney if you want to learn how to write agreements, prepare documents, negotiate terms and deal with conflicts. A litigation attorney must be familiar with the rules of evidence, statutes of limitations, rules of discovery, etc.
Additionally, the differences could be based on the client's location. A New York City attorney may not be as familiar in California as an attorney working in California. A Florida attorney may not be as familiar in Texas with Texas laws, than someone who practiced in Texas.