While some would argue that ANY blowjob is better than nothing, I would disagree. Some women (and men, can't leave the gays out, diversity mother****er!) are just better at blowing a dude than others. It would be almost impossible, then, to compare the two as one better than the other, without a side by side comparison. And even then, how do you rate a single woman's blowjob to the machine, if she's no good? This would require many sample sizes of comparison. Since the machine would, theoretically, be the same every time, you would need to simply compare one to many, average the many, and then arrive at a result. This would also need to account for variables like teeth/no teeth, age/experience, race, color etc. Then, testing over time to account for moral elasticity as well as new techniques developed (and perhaps, future improved versions of the blow job machine). Finally, other variables, such as taint massaging, ball handling, insertion of finger(s) into the anus would need to be accounted for.
As a serious man of science, I would sacrifice my self and sperm production for such a study. And not in the gay side.