I've been planning my caster druid a lot lately and from what I've seen around on the forums and people's builds they tend to go Evocation focus, but I can't help but think why? Creeping cold has no save, which is the standard nuking spell, what do people want their evocation saves for? Sunbeam? Earthquake? Myself I was leaning more towards Transmutation for Entangle, even though it's far less efficient than Web, it doesn't seem like druids have a strong CC capability, compared to sorcerors or wizards, that is. I also wonder if druids actually need a spell focus at all? Could always take mental toughness/imp/epic instead, but it would only grant a max 460 SP, which is hardly worth the 3 feats it costs.

The question is: do druids need spell focus feats, and if yes: why transmutation or evocation?