Technically, (if you meet all of the requirements) the fiance visa is a much faster process if your goal is to enter the US in the least amount of time. A fiance visa takes about 8-10 months (on average) to obtain. In addition to the processing times generally being shorter for the K1 fiance visa, the speed also lies in the fact that you could begn the K1 application process tomorrow. With the fiance visa you have to get married in the US within 90 days of entering the county. (You may want to wait to file until after your visit as you may not be allowed to enter once you file the K1 even with a tourist visa.)
For the spouse visa you can expect to receive your visa in about 12 months AFTER your marriage and filing of your paperwork. So, you would not be able to start this process for a much longer period of time.
Even though the Fiance visa is a faster way to enter the country, it is a slower way to permanent residency. After your k1 is approved and your mary in the US you have to adjust status. This process is what gets you permanent residency in the US, but it takes another 6-12 months. If you apply for a "spouse visa" you will get your legal permanent residence without the additional process of adjusting status.
There is another option which is to apply for a k3 visa. This could eliminate some of the wait time for the spouse visa, but you will need to adjust status just like you would if you obtained a k1 visa.
Processing times vary on a variety of factors such as your fiance's state of residence, your home country and probably most importantly the accuracy and completeness of your petition. In other words, you are more likely to get a speedy approval and avoid the pitfalls and delays of incorrect filings if you use an experienced attorney. A consultation with an attorney will help you better understand the more in depth issues like work authorization, cost, and travel that shold be considered as part of your decision making process.
With the K1 and K3 visas, you will need to apply for an EAD to work during your adjustment of status. This takes about 60-90 days. With the K1 you need advance parole to travel outside of the US.
This information is provided solely for informational purposes and does not establish an attorney client relationship.