I'm very happy with my Orvis Silver Label waders. They've done everything I've asked of them. Everybody has their opinion as you said. Simms has a group of die hard fans, but for how much they cost, I hope to god they perform well! To me it's like asking whether a top end rod is worth the money. Sure, it may perform slightly better than the rod available for half the price, but is it going to perform twice as good? I don't think you can go wrong with mid-priced Orvis or LL Bean products, and the customer service can't be beat.
As for your question about wearing hiking boots instead of the wading boots, why? How long a hike are you talking about? I've worn my wading boots for hikes approaching several miles on some pretty difficult terrain and they've done fine and I haven't done any damage to them. I don't see any problem with wearing hiking boots instead and changing before you wade, but I don't really see the point unless you're hiking a long way, and then I wouldn't be wearing the waders until I got to the water anyway. The last thing you want to do is tear a $200 pair of waders while you're hiking through the woods.
My passion for catching fish is eclipsed only by the fish's passion not to be caught.