Having done both of em in the last couple weeks I can say that, at least for me, Mary Austin -1 was a fair bit harder. I completed em both without extra rest or backpedals. I think the main reason Mary is harder is that is has less rest. The 9 minutes between intervals of Carpathian Peak +2 really helped and it felt a lot easier than I was expecting it to be.
Carpathian Peak +2: AVG HR 145; Max HR 166
Mary Austin -1: AVG HR 155; Max HR 176
My LTHR is around 173 and max is 183.
Leconte is on another level though!