For the pro it is just that you'll have a more responsive throttle and then for the con I guess you'll have higher fuel use on the highway and worse wear and tear for the engine if you rev high!
I've done this upgrade in the past, and it really boosts acceleration, particularly if you want faster starts. Just remember that your top speed might drop a bit, and you'll probably notice a small rise in engine RPMs when you're cruising on the highway. It's a fun modification for enhancing low-end power, but keep the trade-offs in mind. And don't forget to check that your chain works well with the new sprockets