Instant messaging apps have sprouted like mushrooms over the years. But, if you want to avoid wasting your time, money, and effort, you’ll want to stick to those that have been tried and tested by many people and proven to be great.

Two of your best options are Skype and Viber. They have become so popular that, more likely than not, you have at least one friend or family member who’s using either of these apps (or both!). But the question is this: if you had to choose just one messaging app, which should you pick? It’s a difficult question to answer, so we’ve created this guide to help you decide.

Account Creation

Both apps have an easy sign up process but have different requirements. Skype will ask you to create a username, which you can use to sign into your Skype account on any device. Viber, on the other hand, doesn’t require a username but needs you to input and confirm your mobile number.

Supported Platforms

Skype supports more platforms than Viber. Both of them can be downloaded in Windows, Mac, Linux computers as well as Android, iOS, and Windows mobile devices. They can also be installed in wearables like Apple Watches and Android Wear. However, Skype goes above and beyond by providing support for BlackBerry, Amazon Fire Phone, and iPod Touch devices as well as for the Xbox One and even for certain TV models.

Desktop and Mobile Versions

Both Skype and Viber have desktop clients and mobile apps. However, it’s important to note that they each have a different focus: Skype started out as a desktop client, which is why its strengths remains in desktop use. This is evident in its desktop solutions like Skype for Outlook.com and chat integration with Office 365. Viber, meanwhile, started out as a mobile application and has stayed true to its roots. It immediately integrates with your device’s contact list and shows you who among your contacts has Viber; this way, you can use the app to contact them without spending too much.

Calls and Messages

Just like with many other messaging apps, Skype and Viber offer free instant messaging as well as free audio and video calls if you make them to people using the same app (i.e. Skype-to-Skype calls and Viber-to-Viber calls). This is great especially if you’re calling people who live in other countries since you’ll get to avoid expensive long-distance rates. Both apps allow you to call mobile and landline numbers that are not using Skype or Viber, but you’ll have to pay a small fee.

Data Consumption

Generally, Skype consumes around 3 MB for every minute of a Skype-to-Skype phone call. Viber, on the other hand, uses 240 KB per minute or around 14 MB per hour. With these, it’s clear to see that Viber has significantly lower data consumption and is a great choice for those who are on limited data plans.

User Base

Skype had 300 million monthly users as of March 2016, while Viber had 260 million monthly users as of December 2016. This 40-million difference in user base means that Skype has a wider reach and that, statistically, the average person is more likely using Skype than Viber. If your goal is to reach as many people as possible, your best bet is to use Skype.

Skype and Viber both have several benefits to offer. To choose the right app for you, it’s important to weigh the pros and cons and pick a messaging service that best suits your needs and budget.