When I bought my wife an ipad, I first backed up mine to be up to date and then activated hers. Everything I had showed up on hers. Now stuff she has can be synced to mine too. The trick to remember is that in itunes on your computer, you need to select what gets sent from your computer to your connected ipad.
The part I'm not sure about is if you delete an ap and then sync, does it remove it from itunes as well? I think it does and then next time you sync the other ipad, I think it would remove it from that one too. With only two devices syncing to the same ipad account, I get confused, lose track of what stays and what gets deleted. I can't image if I had many iOS devices, how do you keep track?
Another issue I have is I may want to keep 30Gb of movies on my ipad which is a 64Gb and my wife may want to keep only 12 Gb of movies on hers, some different, some the same. But her ipad is only a 16Gb. What's the best way to keep track of everything?
One solution I thought would be that your itunes on your computer has everything from all devices synced to that account. Then when you sync a smaller ipad, you need to select only the stuff you want. Not sure if it does this but when you connect the smaller ipad, does it remember what you had before? If you delete from the ipad and resync, will it reinstall it from itunes next time unless you delete it from itunes, it should reinstall it again, right? This gets confusing fast with two, imagine several devices.
Frank, I try to resync my ipad once a week or right after I buy a few apps. I'd do my wife's too but its hard to pry it out of her hands!