Well, we had been planning to do the fiance visa but now actually considering just getting married and then do the marriage visa... Just so much less hassle than applying for multiple visas and also better/easier financially.
That is much easier, and with a spousal visa, you could work and use the NHS for 'free' immediately, neither or which are allowed on a fiance visa.... though you would need to get married in the US or a third country, as you need a visa to marry in the UK.
Just to clarify though, a marriage visa IS a fiance visa. Once you are married, you apply for a spousal visa. There's actually no such visa officially called a 'fiance visa' - that's just what we call it on the internet

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The actual visa names are:
- Marriage visa... valid for 6 months, for the purpose of getting married in the UK. No work or study allowed, no NHS access
- Spousal visa... valid for 33 months, for people who are already married to a UK citizen. Work and study allowed immediately, and full NHS access.