When you have no access, or the wall is higher than the ground, you sometimes have no other choice but to consider some method to move the concrete beyond the end of the chute, such as pumping. If the pour is large, pumping is generally the cheapest way to go, because the labor savings offsets the cost of the pump. On a small pour, quite often that's not the case. On smaller pours, it's sometimes worthwhile to use a small crane and bucket even though labor costs will be somewhat higher.
Convenience is also a consideration. On accessible pours we often use a pump to save time. Also, in many situations the contractors have to add an excessive amount of water to the concrete to get it to flow, and this not only lowers the strength but can create form bulges and honeycomb in the wall if it's not placed properly. However, in most of the work done by our company, slumps are specified at 4 inches maximum and we often find pumping better than shoveling or dragging. It's also worth considering the use of a pump if you have a very narrow opening at the top of the wall. It's sometimes very difficult to get the concrete into the wall. The hose going down in the wall can be a big labor saver because otherwise often a couple of men are involved in placement. The pump hose eliminates the need for a tremie. On one-sided walls the pump will tend to put the concrete in more gently. It will avoid the surges that can happen with a crane or bucket or even with chute placement where you're piling concrete up in one place to flow laterally.
This article discusses how to order the pump, ordering the pumping mix, methods of pricing for pumping, preparing the site, coordinating operations, and monitoring concrete requirements.