I have a 256GB SSD that holds all my needed stuff, and then my libraries both music and pictures, are on external drives.
So I guess I've opted for overall speed, for most of my day to day uses and then have an external drive for the larger stuff.
Given I have multiple devices I'm also finding I neither need nor find it wholly beneficial to store music/photos on every device. That free's up a lot of space, where once my laptop may have had several GB's of photos and music.
Now I have an iPad, iPhone, multi room home audio/video setup and laptop, its just an unnecessary task to locally store and then keep in sync all those libraries on each device.
For music I use Deezer predominantly (comes free with my phone contract), playlists are accessible across all devices and can be streamed. But I largely listen to music on my phone when on the move, which is more efficient then my laptop (in terms of battery usage), or my multi room audio system when at home.
Pictures are stored on home server and streamed, other then a small subset which I keep on all my devices for regular access (most recent trips, screensavers, most looked at pics, etc).
Videos are also stored on home server for streaming to devices/access to each TV in the house. My SKY (satellite TV) package also allows me to stream content to supplement casual viewing needs on the move. And if needed for a trip I pull a couple of movies from the server onto the device(s) I'm taking with me.
Internet access is becoming so ubiquitous (everyone I know has wifi, all work spaces have it, most areas where I'd want to access data have internet access and as a backup I have 4G through my mobile) its starting to become easier for me to just stream casual use data (films/music/videos) and maintain it in one place, rather then keep data on every device in sync.
I still purchased a rMBP with a 512GB SSD, but thats to ensure I have critical data (that which is essential to my work) accessible 24/7 instantly. When time is money, its worth maintaining that data on my computers.