It depends on what you want. "Encyclopedia of Chess Combinations" is for me the pinnacle of a tactics book along with Laszlo Polgar's "Chess Middlegame". There is an abundance of tough exercises in them. You do not get instruction here, just tough and very though exercises.
"1000 Checkmate Combinations" is designed like a textbook where information is given followed by relevant exercises so it has more instructional value. It was published as "Последний шах : Антология матовых комбинаций" in 1979.
Do not forget "Chess Praktikum" (Шахматный практикум) by Jakov Nejshtadt by the way. I think it is in third edition now which was translated into English by New in Chess.
Which is better in your opinion and why !?
Source :
https://www.amazon.com/1000-Checkmate-Combinations-Victor-Henkin/dp/1906388709
Vs
https://www.amazon.com/Encyclopedia-of-Chess-Combinations/dp/8672970659