I think you will find Seachem's Prime an overwhelming favorite with the larger portion of aquarists. Its economical while addressing chlorine/chloramine, heavy metals, providing slime coat protection and temporarily detoxing ammonia, nitrite and nitrate. Seachem's Safe is a even more economical option if you are dealing with larger amounts of water.
Kordons Novaqua and Amquel Plus are actually meant to be in conjunction with each other. Amquel does not address heavy metals or provide slime coat additives. Novaqua does not address ammonia, nitrite or nitrate. The cost for using both is quite pricey, especially if you have large tanks and/or doing multiple water changes. Polyaqua appears to be nothing more than Novaqua with some vitamins. Kordon products in general are no longer carried by many chain stores so accessibility can be an issue as well.
Hope this helps a bit!
Sent from my iPhone using Aquarium Advice