Most of Bethesda's games have been well-fixed by modder's certain Unofficial Patch. Sadly, the same can't be said for New Vegas, there are like 3 of the unofficial patches out there (Mission Mojave, YUP, NVEC Bug Fixes,... or even more I didn't know) which do the same thing: fix as much bugs as possible in one package.

Thing is, instead of download 1 patch and be on your way, you have to choose which one to use between these files. From what I know, each of these mods has its own bug fixes rather than "just same patch with different name", for example: if you have MM but not NVEC, you will miss certain bug fixes that only containted in NVEC, or if you only use NVEC you will miss certain bug fixes that YUP has, and vice-versa.

technically, you can use all these mods at once, but the problem is the overlap issue. Since the point is to fix bugs, it's possible that they conflict heavily with each other (3 patches trying to fix a same bug for example, but hey you have to live with that if you want to have all the bug fixed).

So my question is, which one should I really use if I have to use one? or is it okay if I use 3 at once? (but I'm afraid that's not entirely possible since I encountered more CTDs than usual).

Last of all, I really hope the New Vegas Nexus will have its own "officially" Unofficial Patch some day, so it would contain all the bug fixes in one package

I use YUP.

I did use NVEC for a while, but that was way back when it was called "New Vegas Error Corrections". It is pretty much like MM now, which is little bug fixes and adding unneeded content (Even when opting out of it). When I found YUP, I tried it and I was happy because he really does mean it when it is purely bug fixes.