Look. Go Through that topic and see how many ppl are telling that skytest is great for this. Skytest was also mentioned by Captain Joe on his video about preparation for the assessment.
In my opinion skytest is way better because:
1. you pay one price which is somewhere around of yearly fee for lpj. And have it for ever. So you can stick to this improving your skills over years at your free time.
2. many confirm that these are the closest to vienna test system - which - to have an access you need to be a psychologist, and what is used by most of airlines at their assessements. You can't just buy it. I've been doing Vienna Test few times - if you're from Warsaw then look for Malgorzata Chelis who is aviation psychologist - she has vienna test system then you can also compare it to skytest. It is really close to what you have in VTS. + skytest released lately vienna preparation system so I bet it has even better stuff for VTS to train.
3. it also has great tools to train for COMPASS test (eye-hand coordination, attention test and so on)
What is also worth to mention is that i had pilot jobs subscription somewhere in the middle so I didn't have an access for all of these so maybe if you're ****ting gold nuggets then you will be able to afford that. But for me it is also way better economically to get skytest.