I'll be meeting a friend next week who has both libraries and I'm thinking about doing a comparison video. No promises because this is a business trip but I'll see if I can squeeze something out.
He told me Afflatus isn't a substitute for Berlin Strings and if he had to choose one over the other, he would pick Berlin. He also told me Afflatus is ideal for quickly mocking up parts where the strings are going to be replaced by live strings, where Berlin shines for detailed parts that are not going to be replaced.
I suppose that makes sense, Berlin Strings is hard to beat if you need to go for detail...
Legato...slurred, fingered, ostinato arpeggios, runs, portamento
Sustains...immediate, accented, soft, blurred bow stroke control (with and without vib)
Expressivo...short, long
Tremolo...accented, sforzando, pizzicato
Shorts...spiccato exposed, spiccatissimo, spicacato blurred, staccato bold, blurred
Portato...short, long, blurred
Repetitions...16th, triplets
Martele...FFF
Pizzicato...tremolo, percussive
Double-Triple strokes
Trills...HT/WT accented, sforzando
Hook...tremolos, trills
Playable Glissandi
Pre-Recorded Ocatve Runs
And that's Berlin CORE. I paid $840 in 2015. 40% off is a bargain.