When I picked up my copies, back in the 70s, they were equally problematic for me to find, and still equal in status. I have fond memories of both - MP 2 being important to me as a b/w magazine collector from an early age, ASM 135 as one of the first non-distributed, specially-imported and higher-than-cover-priced colour comics I ever bought; a big UK 35p rather than the newsstand 12p.
I liked The Punisher even that early on, having read ASM 129 in a British reprint annual.
Jimmers' suggestion is a shrewd one, and Punisher m/s 1 is a must-have, as it's the story which really raised his profile and gave him the popularity he still has today,