batikmystique

Simply put, this is the difference.

Orvus is a soap. It is actually made for washing horses (works great at that, too) but the quilt shop variety is relabeled Orvus Quilt Soap and the price is higher. Get it at Farm & Fleet and save some $$. It's just a chemical free, gentle soap similar to Woolite.

Retayne is used to prewash fabric before using it in anything. It sets loose dyes. Do not, repeat not, use it for washing fabrics that have been made into something or you risk setting loose dyes onto other fabrics.

Synthrapol keeps loose dyes suspended in the wash water so they do not settle on your quilt. It's pretty much the same as Color Catchers.
Use Retayne for washing fabrics before cutting and wash fabrics by themselves to prevent bleeding onto other fabrics. After the quilt is completed, wash with Synthrapol. This will keep any excess dyes floating in the wash water and prevent them from setting into the other fabrics in the quilt. Synthrapol acts very much like the color catcher sheets.