Many users are intimately aware of Skype and its ability to offer a cheap VoIP calling service. However, many users are less aware of an interesting rival service named Vonage. The Vonage app is available free in more than 87 iTunes stores.
The Vonage app allows users to make 15-minute calls to people from over 100 countries for between $1 and $2. The rate is the same for both mobile phones and landlines. The system functions primarily through Wi-Fi but users in North America have the added option of using 3G, which could cost more depending on the operator.
Vonage has released a iPhone app that is proving to a be a strong competitor to Skype but both of them different strengths. For example, a 15-minute call to mobile or landline in Spain through Vonage will cost only $0.13. However, Skype’s plan costs only $0.2 cents per minute for landline calls but $0.27 for mobile lines. This is based on a pay-as-you go basis.
While the costs to different type of phones may differ, the best advantage Vonage offers users is simply convenience. Users can pay for calls through their iTunes accounts. This bypasses the need for a special subscription or a Vonage home phone service.
Skype, in comparison requires a full credit account or monthly subscription before making calls. However, both these services are certainly cheaper than traditional mobile operators, which usually charge $1+ per minute for foreign calls made by mobile phones.

If you want the ultimate cost advantage, you will have to comb through the rates each service charge and then decided what you want. For example, if you are calling a particular land or mobile line in a particular country or a particular group of countries, it will be more cost effective to simply choose whichever service provider offers the lowest cost.