It all depends on what you believe about tarot, and how you use the cards.
I use tarot, for the most part, as a way to look inwards. It doesn't matter how the cards are chosen. I will get something from them. I buy only the apps that are, literally, an electronic version of a specific deck. For instance, I have the Druid Oracles (animal and plant) as physical cards and as an iPad app. I find that there is no difference whatsoever in my ability to "enter" the card, to meditate on it, to learn and grow from it. In fact, I sometimes prefer the iPad version because the card images are larger, so I can more easily get absorbed in them. In the apps I have, you do not see the card meaning unless you specifically seek it out.
As for random choice, or universe or whatever, guiding the draw ... I don't worry about things like that. If its chance, then chance will work on electronics or paper. If its some power influencing the draw, I figure that influence can work either way as well. To me its a moot point.
I love the ease of use. I love the brightness and size of the images. I love that I can carry around a dozen decks without the bulk of physical decks. I even prefer not having to shuffle by hand. Very few decks are actually both easy to shuffle AND easy to keep in good condition. With an app I have no fears of damaging the cards, and know that its as random as anything else I can do.
I still enjoy using physical cards at times, but I find that I'm using my apps more often than my physical. Unfortunately, the apps are still quite limited in variety. If all my favorite decks were available on my iPad I would keep very few physical decks I think. I'd gain back a lot of space in my deck drawer! LOL