I agree that in the short term (say 4 years), you are equally fucked should something go wrong. In that regard, I agree with everything @biggy says above, including the fact that reactions are caused by dormant conditons that can show up years later. This is a fact. Hoddle10 made this point, and for this reason he favored PMMA (and actually had it done). I have tremendous respect for him and his opinions and approaches to all things PE related. I can't believe he was degloved 3 times. However, this is one area where I tend to disagree. I don't think because the short term risks are the same that this is a good reason to just screw it and go with pmma, which is truly permanent.
There are definitely risks with ellanse, and we currently only have 2 documented cases, and zero long term cases to look at. Formal studies on ellanse are relatively small. However, it has been used since 2009, and although you can find some complaints on plastic surgery forums with lumps or aesthetics, things like granulomas have been rare. There was one published case I found that said they were the first case reported. Of course, there may be others that were not reported (Dr. Oats had one and I don't think he reported it), but I don't think it's widespread. Furthermore, we're talking about PCL, which has been studied going back to the 80s, and is FDA approved for other in-body applications, like drug release devices, and other implants. I read lots of studies that describe it as very biocompatible, non-immunogenic, and having only "mild adverse reactions". It's being considered for all kinds of tissue engineering applications, and I recently posted one where it was being considered for tunica reconstruction. The science behind its bio-degrading lifetime and properties is well known--if you have the 4 year version, it will degrade in about that time.
So yes, in the short term, I consider the risks pretty close to those of PMMA. The two advantages I see with ellanse have to do with the long term. I am pretty sure someone (I think Smalljay) asked Dr. Gary Alter and another well known doctor about the long term effects of PMMA, and said they were both "underwhelmed" regarding possible health risks. However, let me quote Dr. Gary Alter's response to Cassavantes PMMA study:
"No one knows the long-term implications of PMMA micro-spheres in the penis. I hope we won't be seeing problems decades from now
. As the investigators state, removal of the PMMA is difficult or impossible."
He is literally saying "decades." Well, it's bad enough to have a lingering concern over the next 4 years or so, but I don't want that for decades! Time flies, guys... and although 4 years can be a really long time if you're fucked, it isn't decades. In 4 years or so, the ellanse will be gone, and just how much of the collagen you still have remains to be seen. But should a future method, better than ellanse or pmma come up, you will be in a better place with regard to considering future options. Or just go with ellanse again for another 4 years if it served you well. It will still be more cost effective than HA, although more risky.