What is the difference between bootstrapper and titanium backup as far as backup is concerned?
*keep in mind, I am by no means a dev. This is just how I see it and the processes I use with these softwares.
Think of it this way: Bootstrapper (Clockwork) backups are like taking a snapshot of where your entire system is at that moment. Everything - txt messages, apps, data, layout, etc, will all be the same as they were the day you took this snapshot should you ever need to recover your system (you don't like a ROM or OTA you installed). If you have any issues, just flash back to the snapshot. You should make a backup in Clockwork every single time you mess with the OS without exception.
For example, I just installed Liberty ROM, coming from from GummyJAR, coming from Rubix. When I installed GummyJAR, I took one of the "snapshots" of Rubix, just in case I didn't like GummyJAR could just go into clockwork, click Restore, click the Rubix backup, and bang - right back to where I was prior to installing GummyJAR like nothing happened. To go to Liberty, I downloaded the ROM, stuck it on the root of the SD, deleted the Rubix backup, did a GummyJAR backup, then flashed...again - just in case. I also have a clockwork backup of plain 2.2.3 (or whatever the latest OTA was - I forget...ha), rooted, but unaltered otherwise for when the next OTA hits. This way, just in case anything unforseen happens that cannot be dealt with I can just flash back to this snapshot, click "unroot" in Z4root, and install the new OTA. Also, if I do structual damage (break camera, crack screen slightly) to the device and need to return it, I would do the same thing - Take it back to stock.
Titanium, on the other hand, will create a snapshot of your applications and data (should you specify it to). The benefit of this is that if you are rooted and installing custom ROMs, most require a full system wipe - meaning everything has to go prior to install. What I do is go into Titanium before installing a ROM and do a batch "backup all apps and data" (again, take a snapshot of all my software - Market and 3rd party). Then I flash the new ROM (like Liberty, which everyone reading this should - it is the next level) and re-sync my google accounts when it open. It's like starting from scratch. All you have to do from here is go to the Market, download Titanium backup, open, then run a batch where you "install all missing apps and data". Pow - Your software in back to where it was prior to the wipe.
These tools are invaluable. You should definitely have them both. And again - this is just how I do things. Other guys will re-download all apps from scratch and just start fresh on everything. Me? I'm a huge fan of the Titanium way. Hope that helps!