What is the best way of transferring a Canadian law degree to the States?

Is it best to complete the LLM program there or work for a few years as a lawyer in Canada, and just write the bar exam of the particular state you intend to move to?

The answer to this really varies by what state you want to practice law in. I can speak for New York, since I am licensed there and have firsthand experience with foreign law degrees being accepted by the NY Board of Legal Examiners.

The US LLMs for foreign students are kind of a cash cow and pretty basic, IMO. If you have a 3 year degree from a common law country (like Canada) that was completed in-residence, you do not need to do one of those LLMs anyway - you just need to send in your documents to the NY BOLE, which is free of charge. They will either give you clearance after 4-12 months or tell you how to "cure" your deficient degree. A Canadian law dgree should not be deficient for rule 520. Other states like Vermont and Massachussets have similar rules re: Canadian law dgrees but I know little of them in content. Feel free to inquire with those other states.

The LLM will not prepare you for any state bar exam. Taking a bar preparation course with BarBri or Themis will prepare you for the bar exam. And yes you usually need a law license before you land a job, some exceptions being if you have law license abroad and register as a foreign attorney.

What is the best way of transferring a Canadian law degree to the States?

Is it best to complete the LLM program there or work for a few years as a lawyer in Canada, and just write the bar exam of the particular state you intend to move to?