I had a shimano for ultra light fresh water that was a hunk of junk. However it was not a high end model, so I am not counting that. Like I said, I have tried some other reels that never held up. The Penn's always were stronger with great drags. I have not tried the Shimano's you mentioned so I cannot speak from experience. What I have heard from tackle shops and a friend of mine who had one, is that the Penn's have stronger gears and drags. On a bonefishing trip my father's friend's expensive shimano reel blew out somehow, while my father's trusty Penn performed flawlessly.
I am aware that there are possibly some better reels out there. Van Staal or Fin-nor might be better, but that is another discussion that always leads to great debate. If you can truly abuse your reels by not ever washing or oiling them and have them last even five years then I would stick with them too. I have always had good luck with Penn equipment so I will stick with them for the money. And with simple maintainance, they could last a lifetime.
I would definately check out the Liveliner or Slammer to compare before buying an SS. You should even check out the Shimano, if it is as good as Anthony says it is. Then, buy the best you can afford, because it is even more enjoyable and satisfying to fish with nicest equipment you can.