The "Plastic" on the Danvise is a glass reinforced Nylon, and has a yield strength approaching that of steel. Don't discount it just because it's "plastic".
I've been happy with my Danvice 4 or 5 years (can't remember), with no issues with the plastic parts. I have chewed up the jaws a little bit, but that is my fault, not the vice's.
I love it, but don't use the rotary function near as often as I should.
My advice is to get the best equipment you can afford. If you decided that tying was not your bag, you can sell it for most of what you paid for it.
I hope you enjoy tying as much as the rest of us do.
Kirk
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"In every fight, there has to be a winner and a loser. Unless it's a draw."
Jim Lampley, HBO Boxing