OK, so here's my $0.02.
Convatec is a great company. They were the largest in the world, then last I heard Smith & Nephew beat them out with their acquisition of Santyl.
Every company has their advantages. They have to to stay competitive. It might be nice to order, "Duoderm" and actually get it. With Convatec you do. Or how about access to Hyalofill, a new hyaluronic acid dressing. Or the ability to tap into Convatec's Solutions program. All very good, from what I hear. You might even ask them about their program of instruction on part B reimbursement under the surgical dressing provision, (not under PPS in home care though...).
So, I'd say, see what sort of prices they're able to offer and what else you'll be getting. Certainly your home health agency has needs beyond just good products at a good price. Staff development, educational tools, access to experts, etc might all be negotiable.
I like Convatec. They make great products. You won't go wrong with them. However, I can say that about (at least) 3 other companies.