I have ran MDS and Heelclicker this season. They seem pretty close on start to mid shift out aggressiveness. You cannot adjust that part of the MDS, not that you really need to.... IMHO, I don't feel like the MDS has the top end "push" that the HC's have, in other words, I feel the HC's build more track speed on the big end, albeit not by much. (I think it would be hard for any weight to beat the HC's in that dept....) But the MDS are way more forgiving in the backshift dept. The MDS are more forgiving in changing conditions and to dial in, also Steve provides excellent support.
Right now, the HC's are sitting on the shelf..... but what do I know.... this was all on a Cat....