Autofac is very good, though castle has nice perrequest, perwcfrequest lifetime managers (autocracy had per web request too). Though in castle you MUST register everything, it has nice fluent so I. Things like unity/autofac have better support for child containers. And autofacs disposal pattern is well thought out, and it also supports metadata like mef (Nick who wrote part of mef wrote it, which explains that)
So yeah autofac I would say
Yeah Unity is not so bad to be honest
I use Calcium’s. It does DI with support for circular references. I started writing an adapter for Autofac then realised it has this “okay, everything’s done” Build() method. When you want to register new types and so forth you have to use some extension methods and rebuild. I found that awkward. Apart from that, it seems alright.
I've also come to detest fluent APIs apart from well understood domains, like SQL. But that’s just me. I can’t think of anything else I’d want to use a fluent API for apart from an SQL related scenario.
If you’re using Web API then, from memory, Autofac comes already wired up. So there’s nothing to do. That’s nice.
Calcium doesn't support child containers yet. That’s something I should do, but I just haven’t needed it.
I also used Unity for a long while. I believe, for web stuff, the key is performance. It would be wise, I’d say, to take a look at some perf comparisons.
Anyway, that’s my take.