Ovulation kit tests

Dana • My husband and I have been TTC for 4 years. Two with a specialist.
I've been buying and using the Answer brand of Opk's because they are $15 rather than the clear blue easy which are around $45. 
This month I went ahead and bought both types because we have up to two IUIs left before we move to <a href="https://glowing.com/glow-fertility-program">IVF</a>. 
I got a postive on the clear blue on day 14 and didn't get anything on the answer brand until day 16. 
I'm hoping that timing has just been off during our other IUIs where I've ovulated and only tested using the answer brand. 
Anyone else notice use either of these brands and notice a difference in the two readings?