First off, IMHO you would be much happier with the MBA, as it has all the functionality of an actual computer, while iPads are limited to a certain extent by their iOS operating system, which just isn't the same as using MacOS. Depending upon which model of iPad you would be thinking of buying, the truth is that for a little more money you could have a full-fledged computer, a MacBook Air, and that might be far more satisfying to you in the long run.
The only port on an iPad is the charging port, and so in the absence of a working Mac, the way one syncs the iPad for iTunes, Mail, bookmarks, etc., is through iCloud, if one already has that set up. I use both methods, actually. For the most part, updates and syncing and such are done OTA (over the air) on my iPad, but when I first get a new iPad or iPhone, I still do set it up using my computer, as I don't have my iTunes library in iCloud (yeah, I'm different that way!).
It's been a while now -- since late 2018 -- that I last bought a new computer, and back in 2015, the time before that when I last bought a new computer, prior to doing so I analyzed everything to death, thinking seriously about how I use my computer, what I use it for the most, what I would miss if I didn't have a particular functionality or feature, and what setup would work best for me: a desktop or a desktop replacement. At that point, back in 2015, I was trying to decide between another iMac or a MacBook Pro used as a desktop replacement, and for various reasons the latter won. I was so happy with it that then three years later in 2018 I didn't hesitate, simply bought another MacBook Pro, this time jumping into the world of USB-C and all that, too.
As far as iPads go, I bought the 3rd generation 12.9 iPad sometime in 2018, I think, and was simply replacing an older 12.9 iPad because I wanted the newer features and functionality available. I have not done that with the latest generation of iPad Pros, though, as mine is still working just fine and I've been putting more of my discretionary income into camera gear this past several months and will continue to do so for a while. As for the iPad Mini 5, I had had an earlier Mini and loved it for its portability and when version 5 came along, decided to get one to use when traveling, and it has been great for that. Tucks neatly into a purse or bag and does what I need (I have the cellular data version for situations where there is no WiFi).
So, sit down and think about what you want and expect from a device, how you use it the most, what you use it for, do you take it with you when going out of the house and when traveling, or does it spend most of its time at home? Where at home -- inside, outside in the yard or on a patio or deck with you?
How do you feel about typing on a keyboard? With the MBA, of course there is a keyboard provided, and with the iPad, you have an internal keyboard but many people do not like typing on glass, so they choose to buy an external keyboard, either one of the ones Apple offers that connect right to the device or they do as I do and just use an older external Apple BT keyboard that I already had from a previous computer.....
What do you want and need to connect to the device? As I said, much of what's connected to an iPad is via iCloud, and there is no headphone jack, no other port on the device except the charging port. A MacBook/MacBook Air/MacBook Pro has necessary ports, of course, but even there you have to think about this a bit......
Current Macs no longer are using the familiar USB-A (USB-3) ports; they now come with USB-C ports (or, actually, USB-C/Thunderbolt 3). What does this mean to the consumer? Well, if you have external drives or other peripherals that you've been plugging into a previous Mac with USB-A (USB-3) ports, now you will have to either purchase an adapter or a cable that has the appropriate connections on each end or purchase a new peripheral that uses the USB-C type port. Some external drives come with two kinds of cables now, one with USB-A to USB-C and one with USB-C to USB-C, so that the consumer can easily use whichever is needed, and for those who have legacy machines which they are still using, this makes it easy to put data from the older computer on an external drive with one cable and then put the data on the new computer simply by switching the cables. Some of the external drives I have provided both kinds of cables and that was a real help to me; in other cases I was able to buy the kind of cable I needed on Amazon.
Another consideration is how many ports you actually need on the machine, anyway......For some people two ports are just fine -- one for the charging function and one for connecting a peripheral from time to time, or in some situations, using both ports for connecting peripherals when the machine is fully charged. Other people (like me) actually need more than two ports at any given time so I always go with a machine that has four ports right out of the gate. A lot of times I am transferring data from one external drive to another or am doing something else along those lines and yet still need to have my machine charging at the same time.
Anyhow, some food for thought here..... You are quite right to realize that it probably would be best to have a hands-on experience with any machine you are considering purchasing, even if you do have to wait another month or two. That way you'll know how the machine feels in your hands, how heavy or light it feels, and how responsive the keyboard is when you type on it. Also you'll be able to gauge the viewing experience of looking at and reading things on the screen, too, as that's also important, and how the built-in speakers sound, too. I think all the new machines still come with a headphone jack, but that is something to check out, too.
I hope you have all of your data from your 2012 MBP safely backed up so that it can easily be transferred to a new computer if you go the route of purchasing a MacBook Air.....