TFG, certainly, though I think
DW goes better on Daughters than Errants, though it depends whether your opponent has ways around high
def. If your opponent doesn't have an easy way to buff attack rolls,
Def 17 is extremely durable against most enemy infantry, and means they need 11s to hit. Meanwhile, the
DEF of the Errants only gets pushed up to average levels, while their
ARM goes up to 18. POW 12s, or boosted POW 10s (from charging infantry) will still mince even ARM18 with ease, so Unless they're being shot with POW10s or blast damage, it won't make a huge difference. Basically, High
DEF is better than high
ARM for most single wound infantry, unless you can push their
ARM extremely high. The one things Errants have going for them with
DW is they have a lot more bodies on the field, which is good, but I usually engage with Daughter first, then switch it to the Errants afterwards anyway.
That said, there are quite a few things which make
DEF redundant, and when your opponent has those things, you use
DW on the Errants (or whatever other unit you usually take) instead.
Come along and play Warmachine, 40k, boardgames or anything else! 
