This discussion (which Jim loves to restart every few months) depends in large part on what you mean by "better" or "improved." Lighter is easy to measure, so is cost and to an extent, durability. Comfort, on the other hand, is subjective.

We are fortunate that there are so many choices, but few of us, I would speculate, can afford to buy and try every piece of new gear that comes along or even just spend time shopping and looking at gear, other than online. This is especially true of cottage gear which may only be available online.

When I bought my gear for a trip to NZ in the mid 80's, I bought what a local shop carried. If I was making those choices today, my decisions would be much different, because what I consider better choices are now readily available. I would get a different tent, different stove, different rain gear and boots for starters and a different pack.

What I wouldn't change is my base layer (Capilene which I still have) and depending on budget, my bag (a TNF Cats Meow).

What I would take would be a different stove (probably a canister or another MSR multi-fuel stove instead of my XGK, a different tent instead of my SD Flashlight (a fine tent for that era) and better rain gear (I had first generation lightweight Goretex that didn't work at all). I would also get a different boot instead of my all leather Asolo's which I have replaced with a more modern Asolo. My old pack was a TNF Moraine, I think. Worked fine, not terribly heavy (made with Cordura) but newer ones I've tried have better harnesses. Cordura is very durable and in a place like NZ, that is a good feature, especially if you are traveling by plane, train or bus at times.

One point Jim makes is very valid-unless money is no object, you can spend it replacing your gear every couple of years or spend it doing something else, like actually going somewhere with what you have. I would choose the latter.

To show that new doesn't necessarily mean better, read this-
http://dsc.discovery.com/convergence/everestbeyond/diaries/graham1.html

Another version of the same story-
http://news.bbc.co.uk/2/hi/5076634.stm

However, I bet Mallory and Irvine would have made it back down if they had better boots and crampons, better ropes and protection and modern headlamps.