See Rega Bias 2 cartridge description for basic information.
The Rega Elys 2 is the least expensive of the Rega cartridges to offer three point mounting which means that instead of two bolts securing the cartridge to the headshell, the Elys 2 has three. Three bolt cartridges are uncommon because a given cartridge will only work with a given tonearm and arm combination since there is no adjustability with three points as there is with two. You generally only see this where the manufacturer makes the turntable, tonearm, and cartridge. Linn has some three point cartridges as well - the Linn Krystal and the Kandid cartridges.
The advantage of three point is that the setup is very good without using a setup tractor and an individual does not need specialized turntable setup skills to install. For a person who wishes to install a cartridge themselves or is in an area without a convenience turntable technician available, this is a very nice feature.
Compared to the Bias, the Elys 2 has a little higher specification coil winding, and testing standard. We can easily hear that it is a better sounding cartridge when compared side by side on like tables. The Elys is more refined sounding with a more pellucid midrange and superior imaging.
A natural home for the Elys 2 has always been, is, and will likely be the Rega Planar 3 series turntables, the current model being the Rega Planar 3. The Elys 2 is a little too expensive to put on tables where someone is trying to economize, but on the Rega Planar 3 and Planar 6 it's a superb choice. Pearl Audio has sold Rega turntables since 2003, so we have been through three different iterations of the Rega Planar 3 series turntables and two editions of the Elys. As a cost-performance equation, the factory package of Rega Elys 2 and Planar 3 represents a standard of performance in our store, and one we often encourage our customers to consider.
There is a very strong technical reason to put a Rega Elys 2 on a Rega turntable, and that is that Rega turntables are expecting a 14 mm cartridge height. The cartridge height is the distance from the tip of the needle to the top of the cartridge. Most cartridges are 18-19mm in height. Rega, since they had the luxury of designing table, tonearm, cartridge together, decided to reduce the cartridge height. The reason for this is that the parallelogram formed by is trio is made shorter height by 3-4 mm, or 23-26%. A shorter parallelogram will have less play in it, and therefore fewer losses. This is also why you need to use Rega tonearm spacers under the tonearm when you install a non-Rega cartridge on a Rega turntable.
A last benefit of the Elys 2, and its brothers the Exact 2 and Bias 2, is that the needle is very low profile - it's harder to see compared to say a nude-body cartridge, and because of this a less tempting visual beacon, the smaller humans in a family household may see a less fascinating object with which to play.