Where I used to board had an Electro-Groom available for use. It was okay, but I wasn’t blown away by it (no pun intended!) for what one costs.
For my own barn, I bought the orange Metro vac (not the Vac N Blow) for a fraction of the cost. It came with standard household attachments, such as a crevice tool and upholstery brush. I purchased one of the Dr. Smith’s attachments, but it eventually fell apart and I didn’t bother to replace it.
Once I began blowing dust and dirt out of my horses’ coats, rather than vacuuming, as recommended on CoTH, I no longer needed attachments, and obtained better results.
After several years, I needed a replacement hose. Went to our local vacuum repair shop and purchased a replacement hose for $1/foot. At that price, I bought an extra, extra-long one.
For the money, I’ve been happy with my decision.