The only one I would suggest a 5yr. arm to is either an investor or an individual who will be married, move or retire soon and will want to unload the home in 5 years time.
There are loan programs that have 10 to 15 year adjustable terms. If you might think you will sell somewhere in that time frame go for it. Most people only hold onto homes about 10-15 yrs due to life changes. (They retire, the kids move away and they downsize, they have a job transfer, they get married, they have kids and need a bigger house etc. etc.
Banks may try to offer you a lower rate, but it is only temporary or it is a "teaser" rate. BE CAREFUL! Teaser rates usually last only 1-3 months, then the higher regular rate kicks in.
If you know for sure that you are keeping your house for at least 15-20 years, it will do you well to get the lowest FIXED rate you can find.
By the way, 5.75% for a fixed rate is a GREAT RATE..