For any tool in any shop, I always go extra-heavy-duty. That way, the strength of the tool is never a concern. Portable tools, on the other hand...I go for more "technologically advanced" materials that can be both lightweight and strong. But if it ain't moving around (portable)...go for the boat anchor. Not only will it be stronger, but you'll get better product out of it due to the fact it isn't wiggling around on you - you'll get cleaner cuts, straighter lines, and sharper edges from a solid, stable work surface.
Generally if I'm shopping for a shop tool, I hit the antique shops first. Never know what you might find - and my 1870's bench vise is about 1000x more solid and durable than anything made today. Ditto my hydraulic press, and my drill press.
They don't make 'em like they used to.