You can try to use the signalsmith CLI tool (or whatever they ship as a binary) to check your exact audio material. AFAIK I've not changed the internals of that engine too much instead of just wiring in IPP / VDSP and a few other small performance additions.
You can't expect parity with the sound quality of Elastique though. Rubberband sounds worse in my experience than signalsmith - v2 as well as v3.
There is also another timestretch library on the block - Bungee which has a pro version that claims to be on par with Elastique et al, so maybe that would be a contender.