Kansai airport to Okayama

Is there any reason to choose the bus as apposed to the train (Haruka + Shinkansen) to get from Kansai airport to Okayama?
For example, travel time or cost? Thank you.

Bus -
Cost: cheaper
Time: longer

If you can afford it, take the train - shorter travel time and more comfortable!

You can also take the local train. Also takes longer, but is cheaper and you don't have to worry about your luggage. There's more space in the train than in the bus usually.

Depending on when you come, you should use the "Seishun 18 Kippu" and then taking the local train really saves a lot of money. :)

You don't have to worry about your luggage with the bus nor do you have to worry about train transfers or anything really; just put your things in and relax.No more thought needs to go into getting there. It's also cheaper. I can definitely see the bus being worthwhile for many travelers.

With the train, you have to haul all of your luggage onto it where it gets in the way and transfer trains at least once (depending on which type of train you use). This can be tiring, especially after a long flight.

It just depends on you, your schedule, your preferences, etc. but the bus does have benefits.

but the bus does have benefits.

Yes, and it is the reason why there are 7 buses/day from Kansai Airport to Okayama (Honestly I was surprised to know there are 7 buses!).

Thank you everyone for your prompt replies to my question.

I notice that on the bus company web site that for trips to and from the Kansai Airport they require a reservation. Is this accurate? Is there any way to make such a reservation by internet?

Yes, it's a Highway Bus which always require reservations.

You can just buy your ticket at the airport.
It says:

Purchase your ticket :
[B] and [C] ticket counter in Kansai Airport(06:00-23:00)
[A] ticket counter in Kansai Airport(13:00-23:00)

They also have their own little guide on how to purchase tickets:
http://www.kate.co.jp/pc/e_lim_guide/e_lim.html