This isn't really a "which is better/more secure/more featureful etc". I haven't really used NetBSD much at all, I have always used either FreeBSD or OpenBSD.

What are the differences between OpenBSD and NetBSD? Here are a few I've worked out (without using NetBSD):

• NetBSD came first
  
• OpenBSD focuses more on security and correctness
  
• NetBSD is supposed to run on everything
  
• NetBSD's package manager is super portable, can run everywhere
  
• You need like 5 floppies or something to install NetBSD, OpenBSD only needs 1
  

Any more? Should I just find an old laptop and take the plunge?