Go to the "thread tools" right above your post and select "add a poll'. Then select 3 or whatever number of poll options you want. It's pretty straightforward from there.
Out of the three you mentioned, I would imagine Depends would be more absorbent since they're made for adults. Out of the other two kids diapers, I couldn't get into #7s but did find the Underjams reasonably absorbent. They could handle one good wetting.
As a suggestion, you might be better off either polling a few kids brands or a few adult brands. Otherwise, you're going to end up with results lopsided towards the one adult brand being more absorbent for an obvious reason.
The new Attends diapers with the cloth-like outer barrier are designed a *lot* like some of the modern baby diapers. I've been using them for about a month. They're comfortable, not too expensive ($63 for a case of 72), and absorb a heck of a lot. When you have actual incontinence, a good fit and good absorbancy is really important. The new Attends do a pretty good job on both counts.
Well, that's something that could be expected to happen, those are baby diapers and they are really only designed to hold an amount that a baby could produce, which is a lot less than us. My suggestion is that if you are really planning on actually wetting them, you'd be better off with an adult diaper or at least goodnites, which if you fit in pampers size 7, fitting into goodnites should not be an issue for you.