bgaviator -
Most people do not understand the difference between a "rigid" wall (wide footing and a slender reinforced vertical wall) and a "flexible" wall (small shallow footing) that is actually structural facing of a "gravity" wall. You usually do not build structures on a "flexible" wall, but fencing is commonly done. In the case of a near-by structure, the load of that is converted to a surcharge on the soil, just as if it was more gravity load for either type of wall.
The major construction difference is the amount soil involved. A "rigid" concrete wall requires a large amount of excavation and backfill because of the depth AND distance back into a hill that increases with height. A SRW wall is only about 8" deep plus and addition amount (8" or so) for compacted gravel footing that also provides a horizontal base for starting from. This dramatically decreases the volume of excavation and material movement and traffic.
A "rigid" wall uses a vertical slender reinforced wall that is tied to a wide footing with a overlapping layers of steel reinforcement. The vertical reinforcement is needed in the thin wall because the concrete is inherently weak in flexure and to make up for this.
A "gravity" wall is NOT exactly vertical. The face has a slight batter into the soil that is created by shear lugs on the bottom or top of each block, so there in no tension in the concrete, but only shear, which concrete can handle easily. The wall does move and return in place with the weather (temperature, frost and soil pressure) and provides slow uniform drainage of the usually saturated soil behind a "rigid" wall. This interlocking units still allow some curvature (inside or out side) of the walls. The individual units allow for stepping the wall height up or down at the end to match landscaping needs.
The two are totally different method and the gravity situation is obviously older and proven, but the SRW units provide a structural facing that becomes for efficient since it allow geogrid to reinforce the soil behind in the case of higher walls and in areas of poor soil.
Forgive the parenthesis around "rigid" and "flexible", but being an engineer, I am aware of the major difference in the design, construction and cost of the walls. The "flexible" walls do not move much (fractions of an inch that are usually not noticed) and can return when loads are eased off when removed. The slight movement is why "rigid" structures cannot be set on them because the structure cannot tolerate movement, but fences and landscaping can easily be put on SRW walls.
Since all the major systems were developed in the Minneapolis/St. Paul area they have been expose to severe conditions for over 20 or 30 years. The private and municipal crews that install new or replacement sidewalks usually use then for elevation and finishing problems and routinely build walls up to 4' without and off-site engineering.
Dick