…Or Singing vs. An instrument. I think choir and singing is underrated, and I'm not necessarily saying it is any harder or easier than playing an instrument, I just want to share my opinion: They are very different things and difficult in their own ways. (I will now refer to 'singing' as choir and an instrument as 'band' to save typing)
THE BIG DIFFERENCE: Choir is instinctual, Band is learned.
This makes choir automatically easier, RIGHT? We've all sung, choir is easy, RHIGT? WRONG. Think about it.
The instinctual part of singing means that because I've been singing all my life, I don't know what exactly I do to hit a certain note. Say it's a high D. I know that I need to flip into my head voice, lift my soft palette, create space in my mouth, support the note, and modify the vowel to make the note sound good, but what do I do to actually create that note? I can't consciously say to my vocal cords what to do; I can't direct them to sing the note. I have to trust them to put me on the right note.
So, in band, there is something you know you have to do to create a certain note. (IGNORANCY ALERT!) Like, using a certain fingering and blowing a certain way.
Yes, that's means memorizing all the fingerings and that is one of the hardest things about Band as I understand it.
THERE. In Band, there is a barrier between what you think/read (fingers/hands), in choir there is not.
Because band is learned, you have something that you do to create a note. Because singing is instinctual, there is no barrier between what I think/read and what comes out. This makes it harder to sing harmonies, because there is no barrier between what my brain thinks is right and what comes out.
So, if my brain wants to sing the melody I can't think 'hmm, I need to sing the harmony, vocal cords, I need an A'. My brain thinks the melody is right, and I have to fight the instinct to sing that. It's really hard to explain.
When one plays an instrument, do your fingers automatically move towards the notes of the melody instead of the harmony? That's what happens with singing. So I have to hold down a harmony even though my brain says 'no'.
Now, if you put me in band and someone else in choir which of us would do better?
Probably not me. xD Maybe Band takes longer to get a basic grip on, and that's faster in choir but after you have the basics, truly mastering singing is more difficult? I have no idea, but singing isn't easy.
Also, I would assume that band music is written so that each instrument t can hit every one of their notes, even if it is difficult. When a piece asks me to try and reach a high E, I have trouble, but no damn way am I allowed to sing the octave down.
But it is an enormous task, a true effort to create an excellent.
Everyone has to be on pitch, perfectly matched and in sync. Perfect vowels, not stretched. Clean, crisp, correct consonants, so you can be understood. Chest voice/head voice has to be used properly. Having enough breath for ties of well over a dozen counts in a half-beat. Breathing silently in the correct technique. Good dynamics/ crescendos decrescendos no matter where are in your range. Blend. Singing at just the right tone, pitch and volume to make it sound like one voice. Balancing the parts, no matter how people are in each part, even if the altos are singing ridiculously high and the sopranos ridiculously low, they still have to be perfectly balanced. Nice, clean sound, getting through hard constantans. Perfect rhythm.  Having just the right expression on your face, moving just the right amount, conveying just the right mood to the audience, standing for a long, long time. Changing consonants and vowels and notes and vocal sound in general to fit a piece. Good posture. Lifting one's soft palette, supporting notes. Holding down harmonies. Audiating pitches. Singing with perfect pronunciation in foreign languages. Completely memorizing songs. This all and more has to happen with every single singer every single moment of every single song. It requires immense concentration, skill and practice.
All I want to say is; don't underestimate us!
Both are difficult in their own way, and singing isn't nearly as easy as it looks, or as it is when you're just singing along in the car.

Oh, and i just had a phenomenal choir festival, which sparked this entry.