I can't talk for others but I do have ES18 (3 years old) and E10 (mic less original version of your IEMs).
To my ears (and audio set up + preference), these two have got two very distinct sound signature (quality) to it. E10 to me is more balanced and clearer sounding of the two with better imaging and detail retrieval. ES18 on the other hand, has got overly warm sound signature with loads of mid bass (bordering on bloating) that creeps into other frequencies (mids, in particular). If, i were given a choice to choose between these two (for my interests), i will prefer E10 over ES18.
I would suggest you to try out your newly bought E10S with some of your favt music genres/albums/tracks. If you find them not matching with your taste then go for something else or else stay with E10S. At the end of the day, it's your choice (and audio preference).
Cheers!