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.
As for white vinegar, it does not work for setting dyes these days. It used to, but the dyes have all changed and all vinegar does now is get grunge out of dirty laundry. It no longer works on setting dyes and hasn't for quite some time now.
Last edited by ghostrider; 03-06-2012 at 09:37 PM.