Welcome to Librarium Online!
Say I run 1000 points of speed freeks, it will not be worth getting the lone boss in a trukk a nob bodyguard as this will take up about 1/3 of the points. If I get him a bike however I will lose the backup trukk for falling back to, especially in 1k I think it is an important asset as it's just 1 of 4 trukks.
Remember, your warboss doesn't HAVE to ride around in his own wartrukk. If you wanted to stick him in a trukk with a group of, say, skarboyz, you are more then welcome to do so. Just leave him enough room to crawl in there. Then his trukk can remain in the back as a mobbing up point.
"Some days you're the Mekboy building the kannon, the rest you're the grot being blown up by it."
- Quote attributed to Sorkrates, before his much mourned death due to ingestion of Hemsquig Juice.
"Dis iz my choppa, and herez me gun. Dat's for killin' and so'z dis one!"
- Bloodaxe Kommando Warchant
That's what I have him as now; the Boss with 9 skar boyz 3 of which have burnas. The boss's trukk is backup/fallback. Putting the boss on a bike will cost about the same as the boss in a trukk, however the fallback trukk will be gone. The Boss on a bike however can have a power klaw without having problems with difficult terrain rolls, plus as biker he can break from combat whenever he wants to and go hunting something else (please let me know if this is incorrect).
There are some plus and minus points, but which would be better for a speed freeks army?