Twin tube, and monos can both be good depending on your needs/requirements.
And there is actually data to support twin tubes being better for daily drivers due to their better ability to respond to normal road "noise" such as truck ruts, etc. where monos might tend to "bounce"
http://www.whiteline.com.au/faqshock...haracteristics.
Beleive it or not, there was a good article on this in a recent Compact Car as well.
For your needs, I would stick to the Flex.