if you don't mind me asking, how do you really learn about the different models of concurrency/parallelism well enough to be able to compare them based not only

if you don't mind me asking, how do you really learn about the different models of concurrency/parallelism well enough to be able to compare them based not only on API/programming model but also performance and low-level differences? as an example,i want to build a web crawler. ive worked with akka actors, and that seems like a good fit because the messaging logic for scraping is simple and it gives me remote distribution for free.. but then i see all these other models and wonder - what is the difference in doing it with Rx or futures etc? is there any difference besides choice of programming model in terms of how these things actually map to low level primitives?