I have big vmdk around 1TB
since trial only supports upto 10gb, it will revert to rsync right?
problem is, rsync will resync that 1TB file next time, any alternatives?
Yes, it will fallback to Rsync.
Use OneDiff, although it will not offer you checksum check upon backup completion, which is highly recommendable.
Or just backup the whole VM each time.
XSIBackup-Free is a great tool for home use and learning, but if you have a 1tb. .vmdk file and you want enterprise level cinfidence in your data, I would just by Pro version. It's a perpetual license and you will still have upgrades during one year.