The older VAG-COM\VCDS is better as you can use it on any compatible VAG vehicle. The new VCDS you have to buy different versions a 3 VIN or 10 VIN so you will be stuck on using it on other vehicles.
You can search fleabay for genuine VCDS cables but the only one I've seen wanted the same price as a new cable. I wouldn't advice you get a cheap Chinese cloned cable as they are troublesome and a lot of good forums won't let you post questions about them.
VCDS won't help you change a timing belt only the IQ values. Once you have a genuine cable the software is free to download and install regularly. The
Ross-Tech forum is good if you have problems but make you register the cable online before joining and posting. If you have a pirate cable you will be black flagged and banned.