To elaborate on the technical specialist thing:
In aviation, the CWO is going to be confined to the maintenance department. That's what he did as an enlisted man, and that's what he knows best. More often than not, the CWO is going to be the MMCO (Maintenance Material Control Officer). He's the guy who works in Maintenance Control with the MMCPO and other chiefs to make sure enough birds are up, when inspections are due, etc. His concern is the production of the squadron. (He'll usually be looking at the dry erase board that has the up and down arrows for the aircraft status with a pissed off look on his face.)
How does this relate to you? As an unrestriced line Pilot/NFO, you can hold any job in any department (Saftey, admin, OPS, maintenance), and it's in the best interest in your career development to cycle through all these positions. The CWO doesn't have that concern...he's all maintenance, all the time.
As for why we have both LDOs and Warrants, the answer again lies in the specialist vs. manager concept. The CWO is basically going to hold billets not higher than the squadron or AIMD (Div O) level. We had a CWO3 who was doing his second sea tour as the MMCO, a job he had done as a CWO2. You probably won't see an LDO do that, and if he did, he'd be holding a job he didn't have a chance to do in his previous squadron tour. If an LDO decides to repeat and do say, a 2nd MMCO tour, he won't be competitive for promotion. An LDO is also confined to the maintenance department, but has the mobility to be the CAGMO or AIMD MMCO/AMO. All 3 are O-4 billets that can be held by an LDO or a 1520 (AMDO).
*Disclaimer: This is how warrants play into aviation. I have no idea how they come into play in other communities, and I left out the squadron Gunner, who can be an LDO or Warrant. Good day.