Ovulation Tracking

So I have been using "My Days" period tracker for almost 2 years. And I recently discovered "Glow" on my Facebook page. I've been using it for 2 months now and have found the articles and the community to be very supporting and helpful. But I'm concerned about my ovulation schedule. The first pic is from "My Days". The second is from "Glow". As you can see ovulation is a week apart. I don't know if it's just that "Glow" is more accurate or if "My Days" just knows me better. That being said, I was thinking about getting an ovulation test to help determine when it will happen. And to do bbt and CM monitor at the same time so I understand what I'm looking at. What is the more trusted brand? What kind have you used?