It seems most raids tend to run Chrono tanks, and that often times the idea of Druid tanks gets laughed at or diminished in my experience, and I've had a hard time figuring out why, aside from just established meta making it easier to gear for and build group comps around. In summary, the two main differences are:
Chrono - DEEPS - allows for optimized DPS, primarily by bringing condi druids, and ensuring maximal GOTL uptime vs larger targets.
Druid - EZ MODE - self reliance, and ensures maximum quickness/alacrity uptime for the group vs larger targets. Reactive tanking vs proactive is more forgiving.
To me, the tradeoffs are rather small, since I think condi druid is slightly overrated, and many groups still run magi's druids anyway, so the potential DPS gains may be entirely offset or even worsened with average groups. Additionally, a minstrel's chrono can potentially eat into druid regen ticks, for those who use a regen build (which I think is optimal for healing druids, due to easily filled CA). Also, if your druid is tanking, Minstrel's Chrono becomes wasted gear, and maxed out zerker/commanders can reach ~10k dps pretty comfortably on many fights. I think it's a clear cut easier to carry with stronger heals, at a minimum loss to DPS in all but the best groups. I think it's easier to carry, and in my experience, I've played a lot of druid tank, chrono, and limited chrono tank, and tend to find the pile of responsibilities a Chrono has on many fights already to be eaten into by the additional responsibility of tanking. I'm likely just underexperienced as a chrono tank, but druid tanking is rather simple by comparison, and eases strain on healers as well.
In short, I think it's much easier to carry as a druid tank and allows your chronos to focus on their often myriad tasks of pulls, invulns, continuum split, and focusing much more on keeping boons on friends, while benefitting from them yourself to keep your uptime even higher. Yeah chrono has a simple rotation generally speaking, but I think their utility in every fight, even aside from alacrity/quickness is tremendous, and all but the best chronos will have troubles excelling at.
I think both are perfectly valid, and the DPS gains in all but the most optimized groups are small, but feel free to prove me wrong. Is the EU meta any different?