I'd choose the 350. I have the 350 and 580, step down from the 581, and while the 580 is a very nice knife it can't beat the overall burliness of the 350...imo. However it is a bit of a beast when you take it out of your pocket and open it...it is not like taking out your SAK.
The 350, while looking more robust, is smaller and thinner though heavier than the 580. But when opening them side by side the 350, to me, does look more rugged.
You can't go wrong with any of those you offer.