Sure online greeting cards are easy and convenient to give, but can it beat the authentic nature of a physical holiday greeting card?
Although technology is moving quicker than the speed of light, card giving isn't. Perhaps, the best way to give a card is by exchanging the real thing. So, when you're thinking of giving a business greeting card, maybe you should think about buying business Christmas cards at the store before doing an online search for "online greeting cards".
There's something tangible and extremely personal about sending out greeting cards. If you want to be even more personal, consider purchasing personalized greeting cards for your cohorts. These are the kind of things where effort is directly correlated with how much you care. And when someone sees an online greeting card, it just doesn't have the same effect as some decked out personalized greeting card (other extreme).
Want to give the card with more meaning and simply more "oomph"? Then consider getting a personalized greeting card. At least, you can make it as personal as writing their name on the top of the card and signing your own on the bottom.