Premium Econ AA vs IB TATL

Has anybody experienced both and can provide some pros and cons of AA vs IB, particularly on the hard product? For example, I've read that the AA premium econ bulkhead is actually quite small leg wise? And that AA has four across in the middle?

Also, any disadvantages to flying AA in prem econ out of MAD instead of IB pre econ, for example? And any way to improve the immigration experience at MIA (i.e., do they both go to the same immigration or is one better positioned vs the other)?

Trying to make up my mind on whether we (2 adults, 2 kids) do all AA, all IB or a one of each.

Much appreciated!