Again, there are TONs of info answer the questions you're asking on the forum, use the search button first.
Anyway, the sand won't get into the filters unless the intake is right by the sand. Sand as the advantage of easy planting and very cheap campared to fluorite. The disatvantage is that it doesn't have any CEC, Cation Exchange Capcity, which just means it doesn't hold nurtients for the plant roots. It also can compact which isn't good. However, about 9/10 people IME love thier sand.
Fluorite has high CEC, its made specifically for growing aquatic plants, and won't compact. Disatvantages are high cost relative to sand, and clouding the water - but this part is due to ineffective rinsing. Alot of people use fluorite dust free, and a few don't get it right.