Just to cover the basics, before you rule anything out have you seriously looked at alternatives such as Xsara Picasso
, Nissan Almera Tino
and Honda CRV
or even a Fiat Multipla especially this one
I say this because having rushed into buying a scenic I find myself waiting for something to go wrong and wishing I had bought one of the above.
In my experience the scenics auto gearbox warning light can light up and trying to get it sorted is time consuming and/or expensive. If you can live with it going into limp mode every other trip then you could probably ignore it like me, but to be honest IF you can get a scenic cheaply
then be prepared to spend money getting it sorted out, which is probably good advice for any second hand vehicle but I suspect more-so for Renaults.
Check for damp carpets, warning lights not coming on or going off when they should, electric windows not working and electrical issues.
As for specific versions it's a matter of researching particular features and deciding what you want - for me having the ability to turn off the kids access to the rear electric windows was an unexpected bonus and it's definitely a feature I will be looking for in the future.
I hope this helps a little.