There were two versions of the Excelerators from what I hear. Early ones I think were called Penetrators and not as good as the later (and current) Excelerators. BUT, I think they also call the Excelerators "Penetrators" in the UK, so I don't know what's up with that coil. It's either an old pre-Excelerator that was said not to be as good, or it might be a new Excelerator called a Penetrator in the UK.
If you surf the coil sticky thread you'll find a few thread links on these Penetrators/Excelerators. Nobody seems to say much about them so I suspect that might speak volumes, but I do remember a guy (think I posted a thread link in the coil sticky) saying the 12.25 or 12.5" Excelerator was as good to him as the S-12 and just as light if I remember right.
Personaly since I rarely have been able to dig up any field reports on the Excelerators, I think I'd pass on owning one myself. They have been around for much longer years than the SEFs and yet look at the different in messager traffic.
The 5" and 6" solid Excelerators are a different story though. The 6" version in particular appears to be the top pick for super heavy trash among FBS guys, yet still getting outstanding depth. I think they might have made the 6" for the BBS units a few years ago and maybe they still do in the UK? All these coils are made by Detech- SEFs, Ultimate, Excelerators/Penetrators, etc.