i have the beta version and it didn´t crashed all this time.
Lucky! For me it was about one crash for about every 10 rounds of fight, and about three times as much since I get my new computer.
Among many others, there were two bugs I consider critical in the beta mugen. One caused undetermined behavior of the engine when a helper was destroyed under certain conditions (this caused a lot of the crashes, but other strange stuff could also happen), and another caused a player to end up in an invalid state when both players were in a custom state at the same time (this often caused one, or both of the players to get stuck in a throw, without any way to hit them out of it). Thanks to these two, perfectly coded characters caused those things to happen, making the players think that the character was buggy, as the bugs in the engine were not widely known. (I discovered and reported both of those bugs to Elecbyte, actually, so they were probably unknown to most people.)
Of course, if you like the beta more, it's up to you to use it, but if you do, I can't guarantee bug-free characters for you.