What is that cheaper keyboard you are talking about?
Here we get the sound quality of the Ketron SD5 who is like 3 times more expensive.
Of course, even if the sounds are the sames, we cannot compare hardware arrangers and software arrangers.
It's really 2 options.
Hardware is more stable, and more cable free than softwares (even if I gig today with vArranger without any problems, and install all in 5 minutes)
Today, half of my gigs are done with my old but good Ketron SD1, and half with vArranger.
vArranger is not only a good and stable arranger, but also a very nice tool to create new sounds (layered) very easily, with a nice graphical interface.
I will post soon some demos of my new Ketron SD2 sounds

(+ oriental sounds)
Amazing !!
Also, about the price, there is currently a special offer (6 days left) for group buy when you can get a good reduction.
http://www.varranger.fr/vforum/index.php?topic=52.0 Of course, softwares are not against hardware, but along with hardware
Dan
http://www.varranger.fr