I decided to buy an APB 16 last week and am just getting to grips with it, but I can answer my own question.......

Yes I think the APB Tape sounds better than the 542. It's definitely smoother, has a very complimentary saturation and is more versatile.

I'm essentially replacing my mix bus and summing chain (DBox+, Wes Audio Hyperion and Dione, and SSL Fusion) with the APB 16. It's obviously not a like for like, but so far as far as analog feel, weight and flavour it's most certainly there in spades. The only thing I'm kind of missing from my previous set up with the analog summing. I found the DBox+, although transparent, adds some additional openness, dimension and headroom to my mixes. Other than that, I'm more than satisfied with the APB, I'm finding it can really help bring a mix to life.

Anyone who is in doubt of whether this is real analog is definitely mistaken and if you wonder how this compares to plugins (equivalents)... it doesn't, it surpasses them with ease.