I like both! The new ones are more badass, they have a more purposeful look in my eye. I have recently made a unit for my Oakenhammer force, not yet painted but give me a few weeks. I did a few head swaps, not overly keen on the beard to the ground vibe.
The older models look, well, older. They seem content to stand around, supping a few jars, waiting to get back on the bus to the old folk's home. At least, that's what they look like, try to pinch their bingo cards and you will regret it.
I used to love my square based army, but recently as I have added more to my round based force, the love has gone. I'm not one of those old-metals-are-full-of-character types. In fact, I think a lot of the old metal sculpts are pretty crappy and much prefer some newer stuff. But there are exceptions, and I think the longbeards just about scrape into the exceptions list. But if you were to tell me I could only keep one set, the newer plastics would win for me.
Of course, we are all different, and we are all right. Ask ten dwarfs to name their favourite beer and you would get ten different brews to sample.