My husband used to fly the B737 and then the A320. He said if you could combine the best qualities of the two, that is, the Boeing below 5000' and the Airbus above, it would be perfect.
What's so special about corporate jets? Time, privacy and convenience.
Time - it's your schedule, not someone else's. If you need to be screened (complicated - depends when/where/size of aircraft/ownership etc), then it's usually very quick. Immigration checks are done either remotely or through the private terminal (FBO). If they need to be done in a public terminal, you go to the head of the queue.
Privacy - you can escape the public's gaze for a while or have meetings on board. That also links with time. The FBOs are usually well managed and discreet.
Convenience is the big one. It's usually the closest airport to where you are and where you need to go. If you're a business man with multiple stops that day, you just can't do it on an scheduled airline.
Small tube? Not really. Often with only 1 or maybe 2 people in it. The very small ones aren't meant for long trips and they can operate into airports that airliners cannot even think about going to. Eg Phenom 100, Mustangs etc.
The one I flew until last year was known as a super midsize aircraft. Perfect for flying across Europe or continental USA. It could carry 9-10 pax but I'd say 4-6 very comfortably. Max mass was about 18 tonnes. (~Dash 8-1/200 weight). My friends fly the ultra long range Bombardiers and Gulfstreams weighing in at about 40-50 tonnes. (An A320's roughly 60 tonnes). So... not that small.
It's like the difference between a chauffeured limousine and a public bus. Yes it costs more, but if you can afford it, it's worth it.
One could argue the difference between First Class versus Economy. I've been lucky to experience first class (and business class) on many long haul flights. I've also been in economy on long haul flights. For me, it's worth spending the money on either Business or First Class seats on long haul. Other folks may have other priorities, which is ok.
