Should I get the Nexus 4 or the new google S4?

Nice try - an N4 owner is going to answer first

The S4 came out 6 months after the N4 so it has a better processor, bigger screen, better battery and all the goodies Samsung graft onto their phones. Samsung are also .. well, not too bad at rolling out new versions of Android to their phones.

Having said that, the N4 is plenty fast enough, has a pretty big screen, above average battery and vanilla Android is actually really good - and the N4 gets the updates first.

So the S4 is better, but are those advantages worth $300? To me: hell no! But then I'm really tight . To you? That's a call only you make.

I'm sure you would not be disappointed with the S4: it's a really good phone. On the other hand, I'm still really happy with my N4 - I'm sure you wouldn't be disappointed with it either.

 

In the Google S4, I believe you lose most of the features that you get from Samsung's Touchwiz. Same as the Google One.

The only reasons I'd think you would need the Google S4 is:
-Expandable memory
-Removable battery
-Higher specs

 

Hopefully you enjoy your new device

You might want to check the Nexus 4 subforum as well:
Nexus 4 - Android Forums

 

Considering that updates will not come directly from Google on the S4 I would say you caught a break.