Fido monthly plans is better than their prepaid ones because with monthly plans you don't have to worry about go overboard on your usages on voice and texting. Nowadays, most of the plans with Fido gives you unlimited texting and unlimited calls in evening after 7pm untill 7am on weekdays. On weekends, throughout the day calls are usually unlimited for incoming and outgoing. Whereas prepaid plans will reduces your available minutes for both incoming and outgoing calls. But even prepaid has certain times when the calls made would not reduce your available balance.
One good thing about Fido prepaid plans is that you do not have to commit to a certain plans for a fixed period of time usually one year or two year contract. With monthly plans if you are locked into a monthly plans and then before the end of your contract, you decide to break the contract, there is usually penalties for doing so. Especially if you had taken a phone under that contract, you might even have to end up paying for the remaining balance of the phone you got from Fido.