Pros/Cons of using 1 or 2 iTunes accounts for my wife's PC and my PC

To first answer your two questions:

1.) Yes, if you use the same account it will make reccommendations based off of any purchases made from that account.

2.) Yes, even with music purchased from seperate accounts, Home Sharing will allow you to transfer songs. In fact, there's even an option to automatically download purchases from your other computer(s) as they are made.

If this doesn't speak for itself, multiple accounts and home sharing is the way to go. Before, there was DRM-protection on purchases so maybe that steered people away (although you still could authorize multiple computers) but now there is no DRM protection, so any purchases on one computer will play on another no problem, and this is facilitated well with Home Sharing, which allows you to connect up to 5 computers. (For Home Sharing, you sync multiple computers up by using one account, it doesn't matter which one though)

Plus multiple accounts has many other benefits too, like being able to easily have seperate billing info/credit cards.

There have been some sad posts here on AD about divorced folks not being able to get to their purchases. I'm just sayin'. That's one reason for separate itunes store accounts.

Don't quote me on this (I don't have an iPhone/iPad/etc. and never bought an app - so yeah, real credible right? haha) but I am kind of certain that Apps are shareable as well: HOWEVER they might be protected, meaning if you buy it with your account for example, your wife will need to authorize her computer with your account's login info. This shouldn't be a problem for you though since each account can have up to 5 authorized computers.

I'm also not sure if Home Sharing will work with apps (it might), but worst comes to worst you can transfer the files via e-mail/usb/home network.

Again, someone can hopefully confirm this for you...