As the proud owner of a Sig P238 (one that works well, I'd add) I wrestle with this a lot.
There are two bottom lines that I've come up with here.
One: the sig-sized .380s are so easy to carry that there is every opportunity to go armed with one. Given, say, a government model on one side of the equation, and nothing on the other, the Sig is a lot closer to the big .45 in effectiveness than nothing at all, and a lot closer to to nothing at all than the .45 when it comes to carry ease. That makes for a good trade off on paper.
On the other hand, two: when I sit down and imagine a situation where I really have to go at it with a determined attacker, I get this rock in my gut. I like that Sig a lot, but I think I like my 3" J with the old FBI load a lot better, if we are *really* talking gravest extreme scenarios. .380 is just not a lot of stopping power. It will eventually murder archdukes just fine, but I just don't like the the idea of relying upon one for rapid incapacitation of big, hardened, mean and/or drugged up people.
YMMV.