The most important consideration is the kind of music you want to play. You simply want the best tool for the job you have in mind. Nylon strings allow for prodigious control of color, vibrato, and timbreCdue in part to lower tension. They also have less sustain the notes die out more quickly. This may be considered a drawback, but it results in a distinctive percussive quality.
Steel strings have ringing sustain and a sharper attack.
Classical, Brazilian, and flamenco players tend to choose nylon-string guitars. Bluegrass, blues, and pop guitarists are more likely to play steel-string instruments. If you want to be able to bend notes, you ll need steel strings. Altered tunings that use lowered pitches work best on steel-string guitars. Before you buy, think about your goals and then try out as many different guitars as you can.