That is a weird question. Its like if a painter asks" I got blue paint and red paint do you think I need yellow or green?". The distressor along with the 1176 and LA2A are just different colors in your pallete. Only you can really decide what you need. A lot of factors are involved. In my opinion just throwing it out there(I got all three and others as well), a Distressor is a great all around tool. There are some situations where only it works and the others just don't cut it. Does it justify it over the others, sometimes yes, sometimes no, again its up tp you. I will tell you that I am a happy man that I have all three to choose from in different situations.
I would rather have a pair of one of the three, than one of each. I can't stand not having things in pairs, I always feel held back. I would say of the 3 compressors the LA-2a specifically is the least practical. IMO go for two Distressors first, it's a good education in what compression can do and how to pull various tones from your sources through the various side chain functions, distortions, and different classic compression "emulations".
If the tube thing is not a big deal, a pair of La-3a's can be a great value. Many people seem to compare the 1176 and Distressors (even before the recent mod), but the 1176 is not linear (it is dependent on the source according to how it reacts) where as the Distressor is (at least in every other mode besides el-op). The basic fundamental tones of the units are completely different too. Good Luck!