Vocalign Project is good if all you want it for is plain voice over work, or quick time alignments on well tracked vocals and instruments. But that is all it does and is relatively the one trick pony. I say "well tracked" because it can't do anything with volume or inflection differences, it will just align the parts (albeit very well), but that's it.
However, if you want it for a wider range of tasks, such as imparting inflection, pitch and volume matching, you will find Revoice Pro 3 far more useful. It is only slightly more expensive than VocAlign Pro4 and IMO the extra features are worth that whole 25 euros!
If you want to know why Revoice costs what it does? These are just my thoughts of course, but I see it justified by doing exactly what it says on the tin! It handles all matter of vocals, including heavy fry/shouted sounds, without artifacts and gets it right 95% of the time. You may occasionally have to go in and manually rejig a few things, but more often than not it gets it scarily on the money! If you deal with entire songs of twin, or triple, or quad tracked parts, it will save you so many hours of pain staking, manual time alignment, you won't know what to do with yourself.
So it really depends on what your uses will be and how often you will use it, as to whether you can justify the big brother pricing?
It looks like you have been to their site already but in case you didn't see this, check out the comparison chart:
http://www.synchroarts.com/compare