user19986: Ideally I'd like a 2.8 inch and it to be touch screen. 
But most of all I'd rather it work on both boards without much hassle.

user30236: Well any display can work on both of the boards if you can adjust the voltage levels right there is a display which was made for old Nokia phones and it is called nokia-5110-3310 and  is dirt cheap display and it can be used with both Arduino or raspberry pi or any other board which support the protocol here is a link for quick reference. 
Adafruit link to the library 

19986: <p>Ideally I'd like a 2.8 inch and it to be touch screen. 
But most of all I'd rather it work on both boards without much hassle.</p>
 30236: <p>Well any display can work on both of the boards if you can adjust the voltage levels right there is a display which was made for old Nokia phones and it is called nokia-5110-3310 and  is dirt cheap display and it can be used with both Arduino or raspberry pi or any other board which support the protocol here is a link for quick reference. </p>

<p><a href="https://learn.adafruit.com/nokia-5110-3310-lcd-python-library/overview" rel="nofollow noreferrer">Adafruit link to the library </a></p>
