Sn has hardly ever been reported to be painful but discomfort has been reported. I've seen people say the feeling and taste are not bad. It's a bit of a range of experiences.
It's known to cause nausea, vomiting, and tachycardia. You can take medicines to alleviate discomfort but it might still happen to some extent considering what it does to the body. I personally can't stand vomiting. N causes less discomfort and you're likely to fall unconscious sooner.