Upgrade OSx & Rebuilding a disk from a Time Machine Backup? Stable Solutions?

Is it best to start from scratch (wiped clean hd) or possible and good enough to Rebuild a disk from a Time Machine Backup and then upgrade the Osx?

There are a few possible scenarios I see.

First of all I have a hd in my Macbook Pro 5.1 which has 10.5.8 OSX this is on my "primary macbook pro".

On it are all the apps and files which I use on a daily basis.

Now I need to upgrade the system to Snow Leopard and then sequently to Lion Osx. That is my plan (not sure if Lion is a good OsX but probably Snow Leopard needs to be upgraded too).....

These are the options I see so far. I would like to be safe side. First I would like to test if the apps and setup are working on a similar Macbook Pro (I have 2) after the upgrade of the OsX.

Suggested procedures:

A.) Go ahead and install a similar hd (as in the primary mac) in the other similar macbook pro and then just if possible restore from the Time Machine Backup from my Primary Macbook Pro to this drive.

B.) Make a clone of the Primary Macbook pros hd (but why should this be any better when I do already have a Time Machine Backup)?

Now which solution is the best when the target is to maintain data integrity and stability of use are of importance?

I am not an expert there are probably other solutions too.

Please advice.