One really helpful fact is that you can back up digital games to PC/Mac, so when you want to put them back on your vita you just have to wait for the time it takes to transfer via USB as opposed to the considerably longer time it takes to download the game fresh from PSN. And with PS+, your saves are in the cloud, so it cuts down the time to get a game back up and running on vita.
That said, I still love having as much of my digital library as possible on my device at any time, as I am very ADD with what I want to play at any time. For example, today I decided to play Velocity Ultra again (a game I hadn't played in over 3 months) to get ready for Velocity 2X but I was on call at the hospital not near my PC. Luckily, I still had it on my 64 GB card. This freedom to play a random game I haven't played in months is one of the reasons I love digital games on handhelds.
Also, PS+ doesn't help the memory woes, especially with the 2 games per month plus like 2-3 more each month via cross buy!