I've only been playing these games for little over 2 years so my sample size isn't huge (probably a few dozen I could stomach long enough to finish or be current on), but when i found Eternum the thing that immediately blew me away was the production value... so far beyond any other adult games I've seen so far, that before I checked Caribdis out & started subbing, I was actually wondering if it was developed by a team of techs in a legit studio somewhere. I felt the same way scope & concept-wise... what a brilliant idea & imagination! It's a universe of potentially infinite worlds, adventures, plots & impregnations.
Yeah the MC is kinda cringe, and with all the blood it must take to operate his clam-stretcher it's no wonder he ain't the sharpest, most eloquent guy around... but every time one of those lonely, love-starved LI's start to bounce around i forgive him.
I admit that i found Eternum first and just finished catching up so I haven't started OIALT yet, though I'm about to (kinda how I got here). As much as much fun as I had playing Eternum I can't do a comparison, but hard as it is for me to imagine I'm actually hoping you're right that OIALT's even better. Wish me luck!