Have a look at each, and pick the one you prefer.
First of all, look at an airfield you know well, such as the one you did your training at. Which guide's representation of your home airfield do you prefer?
If you only plan on going to licensed or well-known airfields, that should be fine, but if you think you might like to visit the occassional unlicensed strip, have a look through the guides to see which contains more of the strips you're likely to visit.
Then buy whichever you prefer.
FFF
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