Bigger Memory Cards Versus More Memory Cards
Periodically, I succumb to the insanely low prices to be had on compact flash memory cards. You've probably at least been tempted yourself. The obvious question to be asked when considering such a purchase is whether it's better to carry fewer large capacity memory cards or a greater number of smaller ones.
Given that there appear to be two diametrically opposed options here, it naturally follows that there would be two diametrically opposed groups advocating those options. This tends to be a topic with strongly held opinions.
On the one hand, fewer big cards mean less to carry around. Some shooters, especially those shooting jpeg only, could easily get a single card big enough to last an entire day or even an entire trip. As megapixel counts continue to go up on new cameras, photographers who shoot raw will be more likely to need more cards. But the number needed obviously has a direct relation to card size, and bigger cards mean fewer cards. On the flip side, losing one of those big cards would clearly be a bummer since it would take with it a greater number of your precious images than would a smaller card. The age-old adage of "putting all your eggs in one basket" comes to mind here.
But both of these positions seem to oversimplify things to me. Let's start with what can actually happen to a memory card.
What people most often fear is that they'll put a memory card full of images in their computer to download the contents only to find that the card can't be read. Or that they'll turn their camera on with a half-full card already in it and find that their camera thinks the card needs formatted when it shouldn't. The cause of such problems can vary but the probability of any well made card failing is likely to be roughly the same regardless of capacity. In order to fit more gigabytes in a card they build it with denser capacity chips, not more chips. The controller circuitry doesn't get duplicated to make a card hold more either. And what about losing a card? A correctly made memory card should last a long time, but even the best brands don't change your odds of dropping a card in a swiftly flowing river or over a cliff. And if you keep all your cards together, you could lose the entire card wallet not just a single card. Given this, it would seem that your chances of having a failure have at least some relationship to the number of cards you have.
Indeed, if you have enough cards, one will surely fail. It's a basic matter of probability. Cards do fail eventually and this includes the ones you own. So while the consequence of losing the images from a bigger card are clearly worse than from losing a smaller one, the likelihood of losing a card at all regardless of size goes up the more cards you have.
A photographer who really lived by the dictum of not putting all their eggs in one basket would have a hard time indeed. Think about this for a minute. Most folks live in just one house or apartment. Most drive around in just one car to get to where they shoot their images. They bring but one camera with them and only one of each lens. Obviously the reliability of the basket in which you put those eggs can increase one's confidence that it won't fail at an inopportune time. And even the most paranoid among us has to trust something.
Bigger memory cards aren't necessarily a problem if they are reliable cards. If you stick with major brands such as Lexar or Sandisk that have a proven track record of reliability you'll reap the benefits of their quality manufacturing methods. If you shop around of the cheapest off-brand you can find you will likely get what you pay for. I tend to be more concerned about buying a quality brand than I am the size of the cards I buy.
That doesn't mean that capacity is irrelevant though. The highest capacity cards tend to be the newest and such designs have yet to be field tested as much as last year's models would have. Had there been an engineering defect in a card first offered last year it would likely have been resolved in samples purchased this year. Cards new this year may not have all the kinks worked out until next year. Buying the biggest cards possible means buying less well tested card designs. You also tend to pay more for the privilege of having bigger memory cards than anyone else. Prices per gigabyte tend to rise disproportionately at the high end of the capacity scale. The sweet spot for price tends to coincide with buying one size down from the bleeding edge, so the very same cards that are likely to be the safest to buy are also the lowest cost per gigabyte.
So rather than going for the biggest cards possible or settling for smaller capacities but more cards, the answer for me lies somewhere in between. The happy medium is where it's at for me.