The regular M1 5W30 has
KV 40 = 61.7 cSt
KV100 = 11.0 cSt
HTHS = 3.1 cP
Sulphated Ash = 0.8 Wt%
Phos = 0.08 Wt%
PP = -42 C
FP = 230 C
Density = 0.855
The M1 5W30 HM has
KV 40 = 72 cSt
KV100 = 12.1 cSt
HTHS = 3.1 cP
Sulphated Ash = ? Wt%
Phos = ? Wt%
PP = -39 C
FP = 230 C
Density = 0.856
They are both now API SN, so I assume their Zinc and Phos limits would be similar.
Interesting they both have the same HTHS, but the HM has a higher KV100. Unless you need extra seal conditioners, it makes me prefer the regular M1 5W30.
My pick would be the M1 10W30 HM (for temperatures above 0F)
KV 40 = 78
KV100 = 12.1
HTHS = 3.5
PP = -39 C
FP = 232 C
Density = 0.861
You get a lot more HTHS for your KV100 and therefore less polymer VII in your oil.