In terms of length, Eroico is shorter than Kurovadis. However it has more CGs, 15 to Kurovadis's 9. There are a total of 3 levels, and 15 enemies with animations. Use that to consider if you feel like buying it or not, but also keep in mind that it will be funding the next game, as usual.
Buy the full version
(Make sure you download the updated demo first, since it's required anyway, what you're buying is an unlock file)
I really messed up V4, so hopefully I fixed the problem in this version. If you downloaded V4 and lost progress, simply go into the prog.dll file with a text editor and set all the 0's to 1's.