Their coverage is lower compared to MTN but they have some of the best deals.
Personally, I'd recommend Tigo for people who need to make many calls and Airtel for travelers who consume data heavily and are staying within major towns and cities in Rwanda. The standard rate for Airtel data is RWF 50 per Mb.
Where and How to Acquire a Sim Card In Rwanda.
You can easily find sim cards all over Kigali.
Network providers have to collect your personal information before registering your sim card so you must carry your passport.
They'll also collect a copy of your passport so carry a copy in as you go to get your sim card.
After the attendant fills out your details on the computer, they'll give a blank form to fill out your details.
Average the whole process of registering a sim card takes 30 minutes.
Sim card costs: $1.5
Note: Every passport holder is only allowed to get one Sim card. I'm not sure what happens if you want to get another one.