The major difference between OEM and SHG is that the OEM part is minimalistic and skeletonized with only 4 pads of plastic guiding the rack and keeping it from twisting. The SHG part engages the housing along its entire length and wraps around the rack itself, increasing the bearing area hundreds of times over.
The SHG slider absolutely keeps the rack from twisting and eliminates the play that causes wandering, squeaking and rattling that plagues the EP3, EM2 and DC5 chassis family of cars.
These cars also have issues with the rack sticking and being sticky in operation in general and a lot of this can be caused by old oxidized grease. SHG recommends that the rack be cleaned out and the grease replaced with Ford silicone brake caliper grease to help with this issue.
You can easily tell how much more bearing area the SHG part has. The stock part has about 1/16″ wear on each pad which was allowing the rack to rotate several degrees. There is a company in the UK that makes a brass copy of the stock part, but we feel that the brass will dig into the soft aluminum housing and start to wear that out instead.
We feel that Delrin is a superior material to wear against aluminum in this regard. Also, recently a company in the UK has ripped off the design and is making copies. Buy the original!