I play several different instruments, but there are a few that are classified as "easy" that I don't play. Why? Because I hate the sound of the damned things! No matter how easy an instrument is to play, you're not going to get very good on it if you don't love the sound that comes out of it. And I'm not talking about the sound an accomplished player gets from it, but what you are going to be producing during those many hours of playing poorly that you'll have to go through before reaching a reasonable level of proficiency.

I personally think the acoustic guitar is the most inherently pleasant sounding instrument there is. It can be played poorly without driving you crazy. And after becoming proficient on guitar, if you should want to learn a more annoying sounding fretted instrument like mandolin or banjo, you'll already have many of the skills you'll need to make learning it less traumatic.