Hi are you talking about the lowest base plan?
The lowest base plan annually cost $15/30*365 = $182.5. After 10% off autopay $182.5*0.9 = $164.25. This is the annual cost of the cheapest Koodo base plan, which only includes Unlimited Texting and Picture Messaging - there is no calling included. See footnote "The $15 base plan requires a Talk Booster add-on and sufficient anytime minutes in your account to use voice features".
The rogers plan is $120 annually for Unlimited Texting and Unlimited Evening & Weekend Calling (6pm-7am), plus 50 free local day-time mins for the year.
To get the Koodo's Unlimited Evening & Weekend Calling (7pm-8am), you have to get $25 per 30 days, which is 25/30*365*0.9 = $273.75 per year. To save money over Rogers (Koodo is 5c/min, where Rogers is 50c/min during the day), you have to expect to make over ($273.75 - $120)/(50c-5c) = 342min, plus Rogers gives you free 50 mins. So if you make over 392 mins per year, then you save money using Koodo, otherwise Rogers is better (without mentioning its evening starts at 6pm).
You can use the cheapest Koodo's base plan (text only) and buy Talk Booster add-on for all calling (daytime, evenings & weekends). How well does this save money over Rogers? Let's say you call 400 min a year on evenings and weekends, then you are better off with Koodo if you call daytime more than ($164.25 + 400*5c - $120)/(50c-5c) + 50 = 193 min per year, which is likely. If you call 800 min a year on evenings and weekends, breakeven at 237 min per year, which is also likely. Yes you can save here, if you don't call much during evenings and weekends but more during the day.
Conclusion, Koodo's $25/month + Talk Booster is worse than Rogers $120 (unless you call during the daytime a lot). Koodo's $15/month is better than Rogers $120 if you don't call much during the daytime or evenings & weekends.
However, for their usage pattern some people will still come out better with Roger's $120 than any of the Koodo's pre-paid plans + Talk Booster.