Is the Premier worth the extra money? i know both now have dual breaking systems.

Go to Bass Pro. Feel and touch over the reels, play with them and find out for yourself  8-)

This didn't really answer your question though. But I can't tell you because i dont own either  8-)

I don't own either of these reels, some say the STX is better and some for the Premier and some even say they are pretty much the same reels but they got the Premier cause it is 2.1 ounces lighter. I would get Premier

I have both reels and honestly the Premier is a much superior reel.  Lighter, smoother and the drag is outstanding.

Later,

I own two of each.  I think the STX performs as well as the Premier but the Premier has some additional subtle features.  I'm not convinced the EVA foam pads on the handle is the hot deal. Both cast exceptionally well and the drag on both is tremendous. I will admit, the light weight of the Premier feels amazing during use.  I would have not believed it.  The advice of putting one of each on a rod and just handling them will be the telling factor.

I only own the Premier's. I gather the STX is just a heavier version of it, so it should still be a great reel. I guess it comes down to if the 2+ ounces are important to you. I have some heavier reels in my lineup, like a Calais DC. And it's sure noticeable when I put it down and pick up a rod with a Premier on it. But I can't say the lighter reels make any difference to me as far as fatigue vs the heavier ones.

Still, if it were me, I'd spend the extra on the Premier again.