It produces the cleanest possible order. A buyer selecting products from your catalogue at your price list means no extraction step, no matching step and no review step, and nothing to get wrong because nothing was interpreted. Every other approach on this page, ours included, tries to recover that quality after the fact, and a recovered order is never better than one that was right at source.
It has no per order cost. Once companies, catalogues and price lists are configured, an account can place a thousand orders and the marginal cost is zero. Document intake, ours or anyone's, is priced per order because reading a document is work. Volume you move onto a portal becomes free to process, which beats automating it.
It is a better experience for the buyer who wants it: live stock, their own pricing, order history, reorder in a few clicks. It removes a class of dispute, because a buyer who picks the product and sees the price cannot argue later about which SKU was meant. And an order that starts in Shopify with the right company, location and price list reaches your ERP and your reporting with fewer corrections.
So if you can move most of your volume into a portal, do that and buy nothing else until you have tried. If your buyers are enthusiastic about self service, we are the wrong purchase.