Overpresure is caused by hardcore streching anyway, actually any pull on the pump will increase the presure.
I don't think the [words=https://officialhydromaxpump.com/?uid=6&oid=2&affid=98]xtreme[/words] has higher suction, they are both rated at -0,55bar on the official site so I think I'll go for the [words=https://officialhydromaxpump.com/?uid=6&oid=2&affid=98]x40[/words]