Going back to Noname's original question, the simple answer is yes, the prop with more pitch will produce more thrust than one of the same diameter, when both are turning at the same rpm.

However, the 14 x 6 may produce more thrust at lower airspeeds (e.g., vertical or hovering), while the 14 x 8 will produce more thrust at higher airspeeds (e.g., level flight)

This was indicated by AQ-500's experience, above.

Then Noname added that he flew at 9,000 ft above sea level. This is certainly a factor of great influence, mostly because an engine won't produce nearly as much power at that altitude, and also because the prop will be about 1/3 less efficient.

At your altitude, the best combination may be the larger engine with the smaller prop. I have no experience with high-altitude model flying, except for Costa Rica (3,200 ft ASL), where I believe only minor changes in needle-valve settings were required.

We'll be looking forward to your report after the first several flights. Take a few different props along.