Don't get me wrong here, I love Sigs. I even like the 239 for what it is. But the damn thing is just too big for the number of shots it has. I sold mine to a friend who wanted one, and don't really miss it.
I don't particularly like Glocks, but I have a G17 in the collection as a representative example.
And I'm partial to full-size guns for carry, in which case I've made the choice for years: 226 over the G17 by a mile. I just shoot the 226 better and trust it more.
Your mileage may vary. They're not the same guns made to the same budget for the same purposes. If I restricted my engagements to 20m, I shoot them about the same. Past that, against non-threatening paper, the Glock is literally all over the map by comparison. I don't want to consider it under stress.