What makes the pools different (other than location and size)? Do certain pools have better features for kids? for adults (i.e. pool bar proximity and clear viewing of kids from chairs, etc.)?
Eaxctly. Brermama mentions the 3 bigger pool areas. All those have access to food/drink and are "free form" shaped. Spa Super Pool isn't very good for the little ones; it is a fairly consistent mid-depth throughout so adults can stand easily throughout. On our two last March trips there was a giant inflatable water slide (25-30' high?) on the Tennis Courts next door. Hope it's still there!
Cascades is great for the kids from 8 mos. to 80 yrs. It has a waterfall that the older kids love, lots of curves so it is good for hide and seek or water tag, and the shallowest end (about 2 to 6" depth) has a bunch of sprays that toddlers could splash around in all day. It is big enough to lose sight of the kids from time to time.
I can't say too much about Fountains/Lakes as we are avowed South siders. I've been over there a couple of times; they are nice big pools with the food court/rec center between them. I can't remember too many of the other features.
The other smaller pools on the South side have their advantages too. They tend to be a bit quieter, so if you want quiet relaxation with a quick cool dip, that is often a better bet. They are rectangles so if you are an early morning lapper, you can get your exercise in - hard to do in a free-form pool. You can bring your own snacks/drinks to any pool, but for some reason I feel less guilty about doing it at the pools without the bars
As to patio/balcony, it is probably a matter of preference. We've stayed in a 3rd floor unit, and the only time I was annoyed by the stairs was when barbequing. I think I forgot at least 3 things, and locked myself out of the back door once, having to run around the building too. I really got my exercise that dinner!

Then again, we stayed in a 4th floor with an elevator once and used the stairs more often than not too.