I would significantly favor higher resolution because the relatively minor differences in AA and detail won't make nearly as much impact as higher source resolution for the print. So if it's really a choice between the higher detail settings, or the lower ones with a higher resolution render, definitely go fort he latter. By the way Detail is only going to affect terrain and sky, and only sky if you have defer atmo off, so in the images you've shown, Detail is actually doing virtually nothing for you as there's no terrain (and barely any sky) visible. You could even do Detail 0.1 (assuming you're using Defer Atmo) and get the same quality result, because everything is covered by plants (objects) anyway which will be raytraced regardless. On some of the images you've shown before there was indeed a lot of terrain, which would benefit from decent baseline Detail settings, but I don't think you need to go over 0.5 anyway.
- Oshyan