The first is "pick a niche you enjoy". It's a great sentiment, and it makes sense to like what you're selling, but realistically 'what you enjoy' won't necessarily coincide with 'what sells well'.
Which brings me to the second view point, "go where the money is". If you want to make a full-time income, then it makes sense to pick a profitable niche/product.
So I'm curious, where do you guys stand on the subject?