To answer your question, I'll use my (not so) expert experience with nipple piercings.

I've never had my nipples pierced, personally, but years ago in highschool, and again just recently, I've dated girls with pierced nipples. As it goes, I've noticed with both that they can get arroused for seemingly no reason. I'm not entirely sure, but it seemed simple things, like taking off her bra and exposing them to the air, or even just talking about what I'd do to them would instantly make them hard. I know for certain that they loved having their nipples played with more than any other girl I've been with- especially the last. Her right ring was ripped out , luckily is didn't cause any scaring or damage, but I could tell she definitely enjoyed having her pierced nipple played with more.. though that may actually be result of possible nerve damage, I'm keen to believe otherwise.

At any rate, I definitely suggest getting them pierced! They're incredible fun, both to play with and to be played with. I've considered getting mine pierced for a while and have resolved to reward myself as such when I finally get a six pack of abs.. ahem.. wish me luck xD

Edit: Sorry, I missed your second post somehow.. I definitely love to play with barbells more- I think they're more fun to bite and lick, though I suppose it would really come down to personall preferences. Either way, they both look great!