Hi Thomas,
A DSP's algorithm development depends on its capability as well as how long it's been around. At this time, the ADAU144x ("Sigma 200") series has the largest assortment of blocks, including for loudness comp. However, the ADAU1452 ("Sigma 300") is capable of even more -- sometime in the future it may overtake the -144x.
Although the -1452 presently has no "official" loudness algorithm, you can cobble together your own with blocks already available. It might look like this:
The user volume control adjusts an integer from 0 to 64 (32.0 format on the -1452) which drives two lookup tables. The top lookup commands the volume control block in dB steps. The Loudness Comp lookup outputs an integer from 1 to 5 in descending order, which in turn chooses one of five filter sets in the Second-Order Filter Lookup blocks. These boost bass and treble in increasing amounts. I didn't attempt to match any published loudness curves, just put something in to make sure it works. Same for the two switch muxes shown, which enable control of gain and filters separately -- with both active I couldn't hear the compensation's boost as volume is decreased (come to think of it, that's the whole idea....).
So, the decision to stay with the -1452 vs. the -144x ultimately depends on what you can presently do with either, compared to the increasing capability of the -1452 in the future.
Best regards,
Bob