My experience comes as a commercial and recreational diver,
The key to staying warm topside or below is layering that traps air, therefore I do not reccomend neoprene, also it gets wet and freezes topside limiting mobility, takes longer to don and doff exposing you to the atmosphere (no underwear under a neo suit) also as it ages it loses it's insulative properties,
I do recommend Vulcanized or Trilaminate drysuits because you can add or remove layers of underwear, they dry exponentially faster and donning and doffing doesnt leave you cold, wet and exposed.
Drysuits protect you from waterborne contaminants and marine life, (ever had Jelly stingers between your wetsuit and body?). I have arrived on dive site been given instructions removed sharp objects from my pockets and shoes, donned my drysuit completed the job, towel dry my drysuit doff it and roll it up put on my shoes and gone home with a nice fat paycheck, you can't do that in a Neoprene drysuit.
I can even dive the warm waters of South Florida in my sharkskin or tee shirt and short pants/socks with my Trilaminate (Don't try that in vulcanized rubber unless you like heatstroke) get topside and comfy while other divers are sitting uncomfortably in their wetsuits.
And for repet dives, donning a wet neoprene dry or wetsuit sucks, Imagine that ice diving.
Don't buy a dry suit until you rent and dive a few first, at $800 and up I am amazed how few people have the common sense to do this.
Finally Macho foolishness aside never ice dive in a wetsuit it's just plain stupid, even warm water wicks away body heat the longer you are immersed, no matter what argument is presented to you and what credentials they may have use common sense. Water on skin wicks away body heat faster than air the colder the water the more the body has to work to keep you warm.
(If I offended someone out there...oh well stop giving harmful advice)
Enjoy