LOL...yeah, it can be a bit of odd language to someone that hasn't heard the terminology before.
Different ROMs offer different things. Some people like a stock ROM that has all the bloat removed and that's it. Others want the most forward-thinking, do it all ROM that's cutting edge in it's abilities. And then there are people like me that want to try both.
Stock ROMs that are just debloated versions of the carrier ROMs are the most stable. They're going to give the user that needs stability the best experience, while keeping the things that the phone maker included (such as all the bells and whistles that Samsung likes to try on it's phones).
Custom ROMs, like CM or AOSP/AOKP, are pushing the limits of what's possible. It's all about giving the user the ability to do things the OEM never envisioned (or didn't implement). The problem with these, at least at first, is that they can be a bit unstable and even simple things like the camera may not work correctly. But these bugs usually get ironed out over time until you're left with a ROM that is not only stable, but amazing in it's features.
By having a Nandroid of both of these (a Nandroid backup literally backs up the entire phone...layout, options, everything...thus why it's so large), you can switch from one to the other in just a couple of minutes. So, lets say you're a user that needs the stability of the stock ROM during the work day, but want the bells and whistles of the custom ROM on the weekends or at night. Just boot into recovery and flash whichever one you need and you're good to go.
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I completely get what you're saying here. And you're right.
There's one developer over on XDA that treats his users with such disdain that I won't flash his ROMs, even though they're generally considered the best for that particular phone. I won't name him, but honestly, he's a complete douche.
The worst part is, he has two threads for a particular ROM...one is the development thread and you're only supposed to post thing in that thread that pertain to advancing the ROM. That's it. If you post one little question, you get slammed and shamed. It's stupid. Of course, if you post how great the ROM is and how amazing the developer is and you thank him for his work, he doesn't do anything but say thanks.
The second thread he has is supposed to be for support and questions about the ROM. Unfortunately, if you ask a question in that thread (which is what it's for), you get hit with the "why don't you search?" question or "
this has been answered a hundred times!" It's infuriating and has made me decide that no matter how good his ROMs are, it's not worth the hassle of dealing with him.