Mystery
would be better than an unstable & old version of AviSynth 2.5.8 MT
My point in this thread is ALL existing AVS versions are bad and "old and unstable" 2.5.8 "SVP edition" is the best one for linear multi-threaded video processing.
At least for scripts and functions used in SVP.
I can imagine that for some very complex scripts like QTGMC AVS 2.6/+ are much better BUT not for SVP.