From what I've read from different people who have converted to Islam, there are a few main reasons for most conversions:
1. Muslims and Christians agree that God is self-existent. This means that He does not derive his existence from anyone. Also they believe in Jesus, love him, and honor him. In fact, no Muslim can be a Muslim unless he or she believes in Jesus, on whom be peace.
The Quran teach that Jesus is prophet or messenger from Allah and not a God so Quran denies the divinity of Jesus. The Qur'an says that Jesus was born of a virgin, that he spoke while he was still only a baby, that he healed the blind and the leper by God's leave, and that he raised the dead by God's leave.
2. Islam is a religious lifestyle, not just a quick Sunday morning church visit and a label. Although some Christians do pray before each meal and spend much time with their Bible, etc.many don't in the USA. Islam is something that can't be shunted into a few spare hours. You pray five times a day. Your dress code is affected; even your food choices are explained in the Qur'an. Many converts like it because they feel actively involved and as if they are truly religious. Some people also studied Buddhism, flirted with Roman Catholicism or spent time with Quakers, but ultimately found them lacking.
3. For women, it is a big and welcome change from the "in your face" sexuality of western culture. Women are not required by the Qur'an to veil. They are required to dress modestly and it is *recommended* that they cover their hair. However, most do veil and some go farther with niquab (the face screen) or other traditional clothes. Women dressed like this consider themselves marked as religious women, not easy dates. They don't get hit on. No one gawks at their bodies. They are clearly off limits sexually and many that I personally know say it is liberating not to have to conform to western standards of sexy dress, makeup and spending so much time and money on appearance. You buy a five-dollar hijab, put your hair in a ponytail and cover, wear long skirt and a tunic shirt -you're set.
4. Islam is also growing because many people are not satisfied with Christianity. They feel it is too liberal, too fluid and changes for the culture. Islam on the other hand is more rigid and does not as a whole allow much for modern changes and the whims of society. Many like it because they feel other religions have loose standards.
A person like me who is unfamiliar with Islamic teachings might be surprised to hear that Islam is not a “religion” in the narrow sense used by secular humanists and does not rely upon blind faith to make its case, but rather, encourages to use minds for example, the Qur'an invites to ponder upon the wonders of creation, and challenges with intellectual arguments. Further study of the Qur'an demonstrates that sound reasoning and scientific knowledge confirm rather than contradict authentic revelation and its ability to satisfy the intellect whilst bringing peace to the soul. Also Islam deals with every aspect of life, spiritual and physical; its jurisprudence is based on a creed, instruction on worship, and ordinances regarding social, economic, and political aspects.
That's what I got from Islam-online & Islam way women's board and a few other friends of mine. Stats taken by many college groups say that women convert 4 times more often then men.