any difference?

I use black-mixed color rounded river stones in a couple of my tanks. I like the look. It's different and not commonly seen. I want to try the salt and pepper look one of these days. IMO, black sand would bring out the colors in some fish and corals more than white.
The only con I can see with using black is that light won't be reflected upward. Rather, it would be absorbed in the sand bed below the corals and in essence, reducing the amount of light the corals absorb from below.

 

Unless the live sand comes straight from the manufacturing line none of the bags will have any living bacteria in them. Those bags sit on the warehouse shoulves for who knows how long then who knows how long the bags have been on the pet store shelves. The bags are also completely sealed. This means no air will be circulated through the bag. No air means no live bacteria. You will also be spending more on less sand due to the water weight. You are probably seeing all those creatures and all the pods because your refugium is doing exactly what it should be doing. Being a refuge for normal prey items. Don't waste your money on live sand. Buy a few bags of sand and ask someone for a hand full of sand. Anyway, once you add your LR the LR will seed your sand. Overall, "bagged live sand" is a gimmick that companies use to try to get inexperienced people to buy their products.

Using things such as Instant Ocean bio-spira, Bacter Boost, Organic Sand Boost, Nitromax, Nitromax Marine, Bio-zyme, Bacter-vital, Nutrifin cycle, reef biofuel, Micro Bacter 7, and reef biofuel is also a no-no. They will only work as long as you use them regularly. They second you stop your tank will crash. This is because these give your tank a "false" cycle. When you stop using these products your "natural" bacteria that should be in your tank is not and your tank will not be able to support your stock.

Don't fall for gimmicks. Take things nice and slow and do them right the first time. You will wind up spending more in the long run.