Oh boy, I love edition wars. 5th edition is the best edition since 2nd. I'll never understand people who put balance above fun. (looking at you J.E. Sawyer) 2nd was stupidly unbalanced. And it's the best ruleset ever. One of the things I like about DOS2 is that doesn't worship at the altar of balance. Pyroclastic eruption is insanely powerful and it's the only way I was able to complete a tactician solo against that demon doctor (whose name I can't spell).
I think the issue of complexity comes down to how engaged / immersed in the world you are. If you really like the setting -- like the Forgotten Realms -- complexity is good, you want to have every option. If you aren't really into the setting -- and I wasn't really into Rivelon -- then simpler is better.
