I can only speak for my own situation, and in my situation it was easier for us to get married here in the US versus the UK--it was something we wanted to do anyway, and didn't really see much need in getting a fiance visa just so we could get married in the UK, only to turn around and have to apply for FLR. So, if marriage is what you and your BF plan on doing, doing so in the US can definitely have its benefits and disadvantages depending on your unique situation.
You'll also want to research what the requirements are for the state you plan on getting married in--in Oregon it was fairly simple, just a 3 day waiting period between filing and being able to use the marriage license, and it looks like we'll be getting the certificates within the next week or so. Google the marriage requirements for whatever state you plan on marrying in, it'll give you some idea of what you need to consider when planning everything out.
As for visiting each other, it depends--technically to visit all you would need is your passport, though depending on your situation it can be much more than that. Sometimes people take along paperwork showing they have ties to their respective countries to avoid issues at immigration, but like I said it depends on a ton of factors--mainly finances, and those ties you have to the US.