Would getting married in Korea and filing for an I-130 be best or filing for a fiancé visa and getting married in the States?

The processing times are about the same for both processes. It is really just a matter of preference and whether you will have sufficient documentation of the bona fide marriage.

There are pros and cons to each process. Many believe fiancee visa is a bit faster, but it is more expensive. I would talk to a lawyer about options. Once filed, either way, there are no specific rules about travel and visits, but it will make visiting harder as an immigrant petition has been filed and temporary visitors must show non-immigrant intent. It can be done, but there is just a risk. It really depends on what your resources are - do you have the funds to travel overseas to marry, how important is it to get married with your family, do you see an advantage to your fiance coming in with an immigrant visa (after marriage and based on an approved I-130 petition) if it means that the process might take a month or two longer or do you just want your fiance here and would be okay with getting married and processing your paperwork in the U.S. Remember, whichever route you choose will require that you check eligibility and document the relationship thoroughly. You should explore these options with an attorney.

The fiance visa or an immigrant visa are going to be relatively similar in time and expense, so you will want to determine what will best fit your needs. If you want to marry in Korea with your family, or prefer to marry in the US.

There are pros and cons to each method. If your boyfriend has plans to go to South Korea and wait for the I-130 to be processed with you, then I'd recommend that. If he plans on staying in the U.S. while the paperwork is processed, then the fiance visa may be better. Talk to an immigration attorney about your options. My office handles these matters on a regular basis.

Filing in the United States with an attorney would be the fastest route. It can take only 3 months from start to finish if done right.

It is up to you. There is not much difference either way. Make sure you work with an attorney, my firm handles such cases in New York.