And here's my John Woo review for everyone...
To start, you're a very lucky guy for owning that 2-pack. I've always been kinda squeamish about paying the premium for DVD's but if I had to do it over again, it would definitely be worth the 42 bucks to own those two. Personally, I own VHS-quality VCD's of John Woo's movies to include 
Killer, 
Hard-Boiled, his lighthearted 
Once a Thief, his darker action/gangster films 
A Better Tomorrow and 
A Better Tomorrow II, and his only successfull leap into American film, 
Face/Off (errr...not counting MI 2).
Both movies are full of action but unless you only see the surface of both films, you'll see that they're very different. Call the pair what you want--opposites, complements...whatever.
Though he made movies prior to 1989, for the most part, 
The Killer was John Woo's introduction to the world. The two main characters are complete opposites--a cop committed to fighting crime and the criminal he's sworn to take down in the form of Chow-Yun Fat's professional killer. The story is as good as any Shakespearian tragedy and keeps you thinking long after the movie's finished. On the surface, there's good (cop) against bad (killer) but as the movie goes on, the two extremes are grayed together. You'll never hear a discussion regarding whether the action or story was better in this movie because the two are so seamlessly woven together. And just to reiterate, the climax is one of the better action scenes you'll see for a long while.
Hard-Boiled, on the other hand, seems to be Woo's gift to the masses. No doubt, 
The Killer introduced Hong Kong moviegoers to Woo's mastery of violence as an art and they were hungry for more. Though the story is as good as any American release in recent memory, it requires 
far less thinking. No, 
Hard-Boiled is just one spectacular gun-fight after another followed by something that makes you cheer. It might have been a little over the top, a little too Hollywoodish after seeing 
The Killer.  It's perfect for a day when you just wanna see the good guy kick ass (using his trusty sub-machine gun that is as accurate as a sniper rifle and never seems to run out of bullets 

) while the bad guys get what's coming to them and everyone ends up happy.