No, they are quite different...
Think of SHSH Blobs as a "ticket" which authorises you to install a particular version of IOS on your device. Without a valid ticket there is no way to get that version installed under any circumstances.
You should always save your blobs as "good practice". You never know when they might come in handy. If you are currently using Cydia, it will be saving your blobs for you. You can see them at the top of the Cydia home page in green text. Alternatively, you can use TinyUmbrella to save them to your PC.
The baseband on your device is the modem firmware software, which is normally included as part of an overall version of IOS. That is the software which controls the telephony part of the device. It runs separately from the operating system. iPhones may be purchased locked or unlocked. If you have a factory unlocked iPhone you never need to worry about the baseband or preserving it, since it will always remain unlocked. Equally, if you are perfectly happy with the carrier you phone is locked to then you never normally need to worry about preserving the baseband of the phone either.
However, if you have a locked phone which you are keen to have unlocked, it is sometimes possible to unlock it (depending on the version of the baseband) using software, such as ultrasn0w, or hardware such as a SIM imposter. It all depends on the version of the baseband.
If you are lucky enough to have a baseband which can be unlocked by software or hardware and you rely on the unlock for the phone to operate, it is VERY important that you preserve the baseband. That means you must prevent it being updated when you update to a new version of IOS. Each new version of IOS typically has a new version of the baseband included in it, which will inevitably patch vulnerabilities which allow it to be unlocked.
In order to preserve the baseband, you normally use a tool such as redsn0w or sn0wbreeze to remove / strip the new baseband from the IOS firmware file you want to restore (making it a custom firmware) and then install this custom firmware using a special restore process (using pwndDFU). That will install a new version of IOS but leave your old (unlockable) baseband intact, hence preserving it.
We have lots of useful stickies on these subjects if you need more information. Please read them!
Hope that clarifies.
