The decision can be a big one. If your flexible in your shipping times and are good with letting others handle your logistics a broker can be a good way to go. They typically work with a broad range of carriers from big box national carriers to independents to LTL. They generally do not have their own trucks but source it all out to who ever they can get to take the load. A lot of times they will have areas of the country they work best in with the partnerships they have formed with their carriers. Timing of the loads may very while they track down trucks to take the loads.
With hiring carrier direct it's all them on the line. The responsibility of the loads, the timing, all of it. Its real easy to track down what went wrong in a shipment to. With a broker, do you really know? You may have more timely service hiring carrier direct, also negotiating prices may be easier to. The broker takes his price to an open market and hopes he can run for the price negotiated. If its a bad price your service may be spotty. Your single carrier should never put themselves in that position, thus should be spot on pricing and service. Single carriers come in all sizes so if your long haul nation wide shipper or local LTL keep in mind when you do your own shopping to make sure exactly the needs are being met. If your ok with that aspect of it you could have a great relationship and a carrier for life. One that really gets to be part of your business.