I use both types of the clearblue OPK's. The success rate is all about timing (no matter what brand of opk you use, I prefer the clearblue cause there's no guesswork). When you get your LH spike (depending on how often you test) you have a 12-48 hour window before you ovulate. This is consider the "best day" to conceive, cause you want the little soldiers up there before you ovulate. Your success increases if you've done the deed before getting the spike, in order to do that you have to know your cycle pretty darn well. Even with great timing success rate of getting pregnant is about 20% (that decreases with age. Mines like 15%) per cycle. Me and my hubby do it every other day a week before I'm expecting my LH spike, and then everyday after for 3 days.
My dr. says the key to having a baby is doing it when you have your spike, but also when you dont.
Hope that helps ^^