1st Person Vs. 3rd Person

Something to remember about anyone telling you HOW to write:
It's advice.
The best advice is the type that's most rare: how to write in a market, or business techniques (for instance, never submit a story with italics...use an underline. The editors & typesetters will know that underlined means italics. The reason? OCR scanners hate italics.) Anything on *style* is just a matter of opinion. Often that opinion is based on experience in the market, but alot of times, it's just personal preference, or outdated market information.
Unfortunately, alot of college courses deal in the latter.

I used to HATE first person. Now, it's hard for me to write anything but, because I've become such a character-driven writer.
But your instructor was right, from one angle...it IS more of a challenge to write third person, because each character has to have a seperate voice. Terry Pratchett is a prime example of being able to pull this off, well.
However, you know what's even more of a challenege? Writing 1st person, which inherently delivers a character voice, but still having character voices seperate and distinct with the other characters.

Either is interchangable for me, as you will see with my Character piece, Which is in 1st, instead of my first story, which was in 3rd.

Neither is better or worse. Each has it's own challenges I find. With 1st person you have the difficulty of keeping the character apart from your own thoughts, and making him/her their own person. With 3rd person you have to express the character with actions and diologue that match the character you have in mind.

Each presents it's own difficulties and benifits.
I like 1st person, but find it actually much harder to write in than 3rd.

With 1st person you're in the character's mind, and development becomes more indepth, and thus more challenging.

the best advice is to not follow advice. Do what YOU want to do, not what other people want you to do. Listen to the advice, and do with it what you will.

(the above advice is intended for amature writers, since professional writers are making a living they must learn to write for other people, not just themselves)

It can also depend on the character and the story. A long story in first person from a schitzophrenic can get as tedious as trying to read the entire Illuminati trilogy in one go.

Which voice works best for you?

I'm partial to reading third person voice, because I like being able to get inside the head of every character in the story. On the other hand, a good first person voice can make me see the world through a totally different set of eyes, and that's fun too.

For the purposes of this exercise, however, you can do what you want to do. I've already had some stories submitted in first person, and some in third. Each voice works within the confines of the story submitted. In fact, there is one I can think of that wouldn't work if the voice changed.

I've written in both though most of my stories are third person. I like writing in first to give my story a more "Detective" feel. Either is good though.