Back in the 'good old days', I always used picks, to play pedal steel and electric guitar, except for when I played my classical guitar. Having sold my steel many moons ago, I now prefer to concentrate my efforts on acoustic bare-finger styles, eg. classical & Travis (without picks) etc. Sound wise, metal picks /w plastic thumb are definately louder, but I do like the thumping sound I get with my thumb, without using anything else. Natural nail and finger flesh can also produce volume if you develope the right touch.
I tried playing with long nails, but find I have better control and speed, when keeping my nails somewhat shorter. It's all a matter of personal taste doing whatever suits you best, which is exactly the point, to play music your own way.