Definitely check with the building inspector about fencing. Our municipality required a fence even though we have an AGP.

The difference in price is considerable. Of course, the primary reason is the construction of steel vs aluminum rather than the depth. I would not take the 2" depth difference into consideration when making a decision. It's not going to affect your swimming pleasure. I would consider construction, warranty, and equipment: what kind of pump and filter comes with either of these pools?