As I write this, I am watching the mens doubles tennis match at the Olympics between France and Spain on the new iPad, while my Nexus 7 is at hand should I need to quickly look something up. Both tablets and their different screen sizes have a place in my personal computing toolkit, yet many wish to compare the iPad and Nexus 7 in either/or terms rather than together.

One fascinating aspect of this new personal computing era is how the debate over which devices are better has changed. The differences between computers used to be all about processor speed, memory, and operating system, but now it’s about size, weight, storage space and operating system. In the past consumer eyes glazed over whenever a vendor spewed specs about their computers, but today consumers pay much more attention to the size, weight, and storage space of tablets and smartphones because these particular specifications are tightly aligned to how these devices are used.

If you just focus on the difference in size of the iPad and Nexus 7 display you will miss a very important and related component, weight. Remember, the new iPad is actually heavier than the iPad 2 and pretty much the same weight as the original iPad. The reason why the new iPad weighs 1.44 pounds is because of the large battery it needs in order to power up that beautiful retina display all day. In other words, the screen size of tablets drives how much they weigh, and the Nexus 7 exploits its lighter weight to meet a use case that the iPad does not meet well.

My main problem with all of the iPads is that they weigh too much to hold comfortably in my hands for any length of time. I cannot really read a book on the iPad for any length of time without finding something to rest the iPad on. In contrast, I can comfortably hold the Nexus 7 in one hand for hours, just as I would with any reasonably size book.

On the other hand, the iPad’s larger screen makes it much better for watching video and for reading content intended to be on 8.5 x 11 inch sheets of paper as is the case for many PDF files. Fortunately, for both of these two instances I usually find something upon which to place the iPad.

Weight is not the only way in which screen size defines different use cases for the iPad and Nexus 7, in my experience screen size also dictates different input experiences. I am not going to write a lengthly blog post using the on-screen keyboard of either of these devices, but in my experience, and I believe this to be the case for most people, it is much easier to “thumb type” using the Nexus 7 in portrait orientation than it is to type on the iPad.

I know the iPad’s split keyboard makes it easier to type, but for me, in a comparison between the two, it is easier to thumb type on the Nexus 7. Consequently, I find the Nexus 7 to be a better note taking device than the iPad, and taking notes may be my most important use case next to reading. After using the HTC Flyer to write notes in digital ink for a year, I have concluded that inking is best done on larger screens that approximate the size of a sheet of paper. If the Nexus 7 came with a digitizer I would probably use it, but the ease of typing on it means I don’t lose anything by not being able to use a stylus.

The bottom line is that the size difference between the Nexus 7 and iPad mean much more than a difference in price, the size drives differences in how the two devices are best used. I know that there are many people who are happy with just one or the other and find the iPad’s weight to be something they can tolerate in trade for a better display. Likewise, many people find the 7 inch screen on the Nexus 7 to be plenty large to watch video and read documents. On the other hand, I think it is also very likely for one to own and actively use both devices.

I think the idea of people owning multiple tablets of different sizes and corresponding prices is the only reason why Apple will bring a smaller size iPad to market. If Apple believes people will use small tablets for the same reason they use larger tablets they wouldn’t sell a smaller one and risk losing sales. Right now I doubt that Apple sees the Nexus 7 as a threat, and simply selling a product as a reaction to a competitor is very un-like Apple. Consequently, I look forward to seeing whether a smaller iPad will directly work with larger models because I expect Apple to emphasize how the two work together as parts of the Apple ecosystem.