I think offering unlimited or unmetered space/bandwidth is just a marketing strategy adopted by various hosts to advertise to customers that they don't need to upgrade or worry about going over any limits. It is highly recommended to read the TOS of the host regarding the unlimited/unmetered space and bandwidth before signing up.

Unlimited space/bandwidth is not possible on a shared account, it is a sign of scam. Beware of the host that offers unlimited bandwidth on a shared account he may not last long.

I would also suggest to go on a free trial which will determine the reliability of the hosting company. Many hosting companies offer 30 days free trial offer or money back guarantee, you should utilize this service to judge their capability. In this way you'll be able to gauge their server speeds, technical aspects, response time and attitude of the staff etc.