Really don't know much about SDS drills, don't have one. Have used a couple different ones over the years that belonged to others. If I need 1/2 inch hole or larger I use my spline drill. If drilling holes for smaller anchors I use standard hammer drill. I suppose if I had to drill a lot of holes the SDS would be worth looking into, but I generally do not run into jobs that require a lot of drilling of smaller holes in concrete.
There is SDS-Plus and SDS-Max.
SDS-Plus is the smaller size, usually best for anchor holes, although it does pretty well up to 1". Common rotary hammers like the Bosch Bulldog, the smaller Hilti's and Makita's, and many others use this.
SDS-Max is the larger size, and AFAIK it's in line with Spline. It's just another standard.
Both of them could be called just plain old SDS, but they are very different.