Violin, flute and piano players have no choice. Whether they are left handed or right handed, they always have to learn to play in the same way: The left handed will have to get accustomed to play in a way that was designed for right handed players. However, left handed guitar players are lucky: for them it is acceptable to play guitar left handed. It is even encouraged to do so.
Many left handed guitar students are to imitate famous rock stars like Jimmy Hendrix or blues legend Albert King- both of whom played right handed guitars flipped over. There are several reasons why they did this, and several more reasons why that is not recommended.
The hardware of a right handed guitar is not set up for playing it flipped over. You may never have noticed, but not all guitar strings are of the same length. The length of the strings can vary by as much as a quarter of an inch, with the lower pitched strings having the extra length. If you take a standard (righty) guitar and flip the strings, the highest pitched strings are going to be longer than the lower pitched strings. This will affect the intonation of the guitar, and the guitar will not play in tune, no matter how hard you try to tune it. Hendrix played a right handed guitar strung backwards, but he had a full time technician to set it up this way- an impossible expense for the rest of the guitar playing world.
Albert King played a right handed guitar upside down, but with the strings still strung for a right handed player. This is definitely out of the ordinary, even for left handed players, and it does overcome the problem of knocking intonation out of adjustment. Of course this method of playing has its advantages; but it will make learning the guitar more difficult than it needs to be, by forcing the player to mentally adjust every chord diagram or bit of music. King did not have the advantage of having access to a proper left handed guitar when he was learning. With few exceptions, in fact, left handed guitars weren't popular enough before the 1960's for manufacturers to alter their product lines to include left hand versions of their instruments.
Modern manufacturing techniques and the increasing availability of better quality materials mean that a left handed person can learn to play handed the same way a right handed person would. The ergonomics of most guitars (especially electric models) demands that they be played as they were made. Cutaways are made to allow your fretting hand access to higher frets, which are untouchable if you flip the guitar.
Today, when more and more guitar manufacturers are making left hand version of their popular models, choosing which guitar to get is much easier. Otherwise, choose your left handed guitar in the same way you would choose a right handed one look at how high the strings are off the fret board and how the guitar sounds. A well set up guitar will feel smooth, with no choppiness. In general, choosing to play a right handed guitar left handed is a bad idea, especially today when left handed guitars are getting to be much more available.
