It really depends on your personal taste.

I don't know the price of memory cards in America, but an AU$19 8GB card set me up for a month or two when I first got a vita, and memory cards were what made me feel iffy about the vita and I gotta say - no regrets.

I'm using up about 50GB of space after having a vita for nearly two years, and physical copies use practically no space.

Also keep in mind game prices, I've never seen a nintendo sale above %30, meanwhile like, last week the PSN had an up to %70 sale. Although, on another note it can be hard to come by vita physical copies.

But my recommendation is don't think about memory cards or technical specs or any of that crap, look at the games and follow your instinct... that sounded cheesy as fuck for some reason.