Get Punisher MAX. Although its 60 issues, the stories are quick reads with little in the way of ambiguity.
100 Bullets is so much of a crime drama that its something you need to devote a lot of time to and in some cases, re-read the stories to get a better understanding of what exactly is going on.
I'd personally go with 100 Bullets but only because I absolutely loved it. I liked the first couple of Punisher arcs but dropped it after while. I would say that Punisher is more accessible than 100 Bullets so that might be a better incentive right now, because with 100 Bullets you have to put more energy into it because it kept referencing stuff from the beginning and such.