I agree with George. I've seen some saying that they want a metal lathe because they can't get the fit they are looking for in a wood lathe. Well, a metal lathe isn't necessarily the answer. When I got my first lathe, the bed was cracked and repaired. I knew it flexed a bit, but I was just starting out and the lathe cost $100. I learned more working with that lathe in how to set up and keep tools sharp because if I didn't I'd apply too much force and the flex would come in to play.
When I bought my Griz, it wasn't perfect. But I learned very quickly where the problem lay and was able to adjust it to get the fit on pens that I do now. Now if I can get great fit on my pens with a lathe that some have described as "one of the worse wood lathes on the planet" (as some call all the Griz wood lathes), then why can't you? I'm not special.
The common thing I've seen in all the thread on metal lathes is, the 7x machine are really capable BUT THEY NEED TO BE TUNED. So if you can't tune your wood to get good results, what makes you think tuning the metal lathe will be any easier?
Another difference I've sen in the two conversations. Most people recommend getting the largest/best lathe for what you may eventually decide to make on wood lathes, "If you can afford it get a PM 3520B instead of the jet Mini. Yes, both are nice, and you may only be making pens now, but you'll want to turn a bowl some day." But when people start talking about metal lathes around here, they never seem to think beyond the pens in recommendations.
Now, I'm not the most knowledgeable person on metal lathes. Or wood lathes for that matter. I've looked into the metal machines once or twice before and didn't pull the trigger because the price and the money I had available. Now I'm back in the looking stage as I think I'll have the funds soon. But I'm not looking for a pen only machine, I'm looking for a machine that will allow me to branch out. Heck, I've looked at a couple that I thought "how the H E double hocky sticks will I get that monster into my shop through a Bilco door?" Hopefully I'll have the funds set aside soon and can actually make the dicision.