Before I begin this article, please understand that in no way am I saying the piano is easier than any other instrument. Truthfully, it is one of the hardest: you have to be able to decode the notes of 2 clefs (as opposed to 1_ and use both hands that play different notes, rhythms, and keys at the same time....eventually, you'll have to throw in your feet to push down and up the pedals that lay underneath your keyboard. Although, this may be difficult, learning the piano encompasses the discipline, muscle memory, hand (and foot)-eye coordination, and cognitive thinking needed to play other instruments. In other words, you develop a plethora of musical knowledge that makes other instruments seem simplified.
Don't get me wrong, any instrument you learn whether it's piano, saxophone, cello, voice, guitar, etc. will be difficult at first. Getting used to a knew sound, holding an instrument differently, and the muscles needed for certain instruments all take some getting used to. The key component is your knowledge of the Music Theory and Ear Training you receive from learning how to play the piano.
All in all, we always recommend learning the piano first before any other instrument. Our students that know how to play piano before starting other instruments tend to progress at a faster pace than those who do not. Before you know it, those students have two (sometimes more) instruments up their sleeves!