Of course, there’s never a general “yes” or “no” answer to this question without knowing the specifics of the case, and what the state’s evidence is going to be.
Assuming though, as in most DWI trials in Texas, that the prosecutor’s evidence will come from one or two officers and the videotape, that the defendant did medium to OK on the tests (no one ever does them perfectly), and that there aren’t any outrageous admissions by the defendant on video (“I’m drunk”, “I had a twelve pack in the last 2 hours”), then the general answer in my opinion is “no, the defendant should not testify”.
Remember that the State’s burden is to prove guilt, and the defense needn’t prove innocence.
Perhaps more importantly, you don’t want this trial to look like a swearing match to the jury. Assault cases, for example, can often come down to the classic “he said, she said” swearing match. But DWIs are fundamentally different.
It’s rarely my theory in a DWI trial that the officer is lying. After all, there’s usually video evidence to show exactly what happened before, during, and after the field sobriety tests.
The theory in most DWI trials is going to be that the defendant’s performance on those so-called sobriety tests is (a) not that bad and (b) equivalent to how he personally might perform on them if he’d had nothing to drink. Then combine that theory with the argument that the state has failed to prove guilt beyond a reasonable doubt.
Not only is a defendant’s testimony unnecessary in that situation, it may backfire. It focuses the jury on a “the cop said this, and the defendant said that” theory of the case instead of a basic, criminal law 101 “the state didn’t prove intoxication” argument.