Which currency pair is more tradable in Forex trading and why?

The most heavily-traded currency pair in Forex, by a wide margin, is the EUR/USD currency pair. There are several reasons for this, including:
high liquidity—it is almost always easy to find a buyer or a seller for EUR/USD so entering or exiting the market is quick and not difficult.
Spreads for EUR/USD is highly competitive, so unless there is a very significant economic news event happening, spreads will be low.
The E.U. and the U.S. feature two of the most transparent economies in the world. So, the fundamentals of the Forex pair are more or less out in the open with little doubt or mystery as to what is going on.