Like i have always said, vray is easy to learn hard to master. IMO Vray suits the perfectionist Do not also forget the price difference between expensive Vray and affordable twilight. Each also servers different markets.
VRAY for SU or VFSU now has a billion materials you can now download for free(you are encouraged to donate, so do the civic thing) http://luzindirecta.luxisessentia.com/
For those that use SU as a hobby, go Twilight.
For those that intend on going pro, go Vray.
For those that intend on becoming masters of the pro, go Thea.
*My biggest regret was fidling around with various renders, becoming averagely
good with each. Tip is to demo 2 or 3 within 1 month. Give your self no longer than 2 months
to make a decision. Try to see if you can make a simple push bike in a garage look sexy and real.
*Check their galleries and be wary of post processed images that can skew your comparisons. Look to see if you can get materials easily as well at the beginning. Once you get itchy, you start customising them to your taste and needs. Heck you might
even buy a $2k camera and make your own bitmaps and textures to impress clients/friends! Like here http://www.photosculpt.net/
*Most casual users will take about 3-6 months to completely understand Vray. If you are hardcore and have a high end PC to render fast images in Vray, maybe 1-2 months.
*A new Manual is in the works for the newest Vray. VFSU is developing a lot
Faster now than it did 2 years ago.
*Vray upgrades arenβt free but there are student rates.
*Vray is used in hollywood
*Vray works on multi cores