If i remember right, the intranasal bordatella vaccination is faster acting than the injection, you can have it done relatively last minute if you need it for unexpected boarding or something, but immunity doesn't last as long as the injection. And the injection doesn't last that long as it is.
See for example
has some information I hadn't heard before--they say the intranasal should only be given the first time, and not for boosters, and not if the dog has previously had bordetella. I dont know why, they don't say, but they say this conclusion is based on research--something to look into.
They also discuss potential side effects of the intranasal vaccination--good to know about if you're going to use it so that you'll know why the symptoms are happening.
Here's an abstract of the study referred to in the article linked above. The bottom line is that in this study, the intranasal vaccine was found to not be effective in dogs that had been previously vaccinated or otherwise exposed to bordetella. The researchers recommend that it not be used except as an initial vaccination. I wonder if there's other research that shows a different finding.