I'd be surprised if there was a significant difference, apart from how much wear there is on a multiple-100k-mile engine. I have a 4d56 head, but I didn't have enough experience with the engine beforehand to tell you if it was different.

I only got one because I was redoing the engine (again) anyway. My old head had some ugly pre-combustion chambers, and had been resurfaced at least once maybe twice before. Otherwise it would have been a case of "if it ain't broke, don't fix it". If you are looking to improve performance, I think the first thing to do is to make sure the IP and the injectors are in good shape, and focus on getting the IP tuned for how you drive. Next, get an intercooler. After that, you can play with the turbo adjustments. And so you don't damage anything, you should probably have a pyrometer.