The SRAM GX der, IIRC, is rated at 48t. I think SRAM knew there is a 46t cassette coming up.
An SGS(long cage) SLX der is stated by Shimano to cover 37t max, and has shown to work at 42t with a 25mm B-Tension screw. Adding a Lindarets Goatlink(distributed by Wolftooth Components) is stated to allow an SGS type Shimano derailleur(BTW: Goatlink only works with Shimano derailleurs) to cover 45t. People have shown that using a Goatlink with a GS(medium cage) der can cove a 42t cassette on a 1x system, while only seeing a slight decrease in shift actuation speed.
On the Flip, a Goatlink decreases the chain wrap in higher gears(6 through 10). Where the OneUp RADr cage keeps a good chain wrap of the higher gears while allowing the der to shift into lower geared 40t/42t cogs.
The differences of the two der modification techs are noticeable in function, and in price.
Buy a Goatlink for $20 to clear 42t on an SGS caged der. Or buy a OneUp SGS RADr cage for $40 to clear 42t and have close to original shifting performance.
