What do I get if I install a custom ROM instead of installing new launcher, new phone app, ...?

Question

I have been thinking about installing a new ROM, like CyanogenMod (most probably), but thought it would be a mess to return to stock ROM if I messed it up, plus, last time I checked, not all features are guaranteed to work (camera, tethering, ...).

Now, my question is not about how to backup the old ROM, because I found another solution: as my phone is rooted, why not remove the stock launcher, the stock music app, stock browser, all the Samsung Software Update and Holy Quran and Samsung Apps and Swype and all the apps Samsung forces me to use? These are easy to back up (in case), and I can replace them with a browser of my choice, ADW Launcher (CyanogenMod's one), music player of my choice, keyboard of my choice, etc.

So what does a custom ROM offer more than just custom launchers and widgets and looks? Or is my option "utopia"?

Note: I'm not sure if that matters, but I'm on a Samsung Galaxy Fit GT-S5670, Rooted Android Froyo 2.2.1

Another Note: I read this question and its answer, but the answer there only states things that could be done with a home replacement app...

UPDATE It seems nothing can't be done with apps. It's just easier and faster and more stable to use a custom ROM, that is if the ROM for your device is stable enough.

Answer 1

Technically, as a root user, you can achieve every exclusive thing what a custom ROM offers. But, its not always as easy as replacing home launcher. What if you need to replace kernel for better overclocking support...

A custom ROM is actually pre-cooked out-of-box firmware packaging (with specialized feature). Remember, popular custom ROMs (like Cyanogen Mod) are generally backed by an expert developers team or community. So, even if you have expertise of doing every such things in your rooted device, its very difficult to match a team or community. And, don't forget those nasty bugs and security loopholes...

The main advantage of custom ROMs: Those who have expertise of doing everything with rooted device, generally cook their own ROM. It's because custom ROMs can be deployed to multiple devices. Think how you would port your customizations to other devices... Its a big hassle than cooking own ROM.

Answer 2

Two major cons to simply using a different launcher Vs. a whole new ROM:

1. Custom ROMs often offer a later version of Android than is available for your device from a manufacturer or carrier. No amount of launchers will give you the newer functionality of latest OS versions.
2. Very often removing manufacturer/carrier "bloat" is not as easy as deleting some APKs from /system/app directory. In cases of custom UIs such as Samsung's TouchWiz, or Motorola's BLUR, or HTC's Sense, many of their apps which replace stock core functions (e.g. Phone/Dialer, Contacts, etc.) are interwoven with the system and each other in such a way that simply removing them may cause crashes or other system instabilities. Installing 3rd-party replacements does not resolve anything, since these apps are always running in the background, using up valuable resources.

Answer 3

I have noticed in various ROMs some features which I have never seen implemented in applications (not as smoothly). Some concrete examples:

• Whisper Systems has a ROM that implements "selective permissions", which supply "blocked" applications with dummy data if a permission is denied. It also has "Full disk encryption for your phone" which encrypts the whole device partition.
• CyanogenMod also has something like that implemented at the core, but an application can do almost the same.
• I have seen MODs that add options to the menu that shows when the power button is pressed (reboot, reboot in recovery, data transfer, ...). This, I guess, can't be done with an app.
• Better overclocking support, although it can be done with an app but does not support all devices after all...
• Boot animation is often changed/removed with custom ROMs.
• Customized notifications bar (transparent or not, more or less options, different icons near the clock, ...) and UI (dialogs for example and other form elements, etc.)
• Customized unlock screens, screen on/off animations, ...

This what I have seen so far.

EDIT To my surprise, as @SachinShekhar pointed out in the comments, ALL this can be achieved with applications, so disregard this answer, I'm leaving it for further reference, if someone turned out to not know about all this... (like me)