Chris Blattman considers some of the pros and cons of being a field research assistant for an RCT: 

Cons

1. It’s getting harder to distinguish yourself from the herd. JPAL and IPA and other field experiment outfits have exploded in size. Whereas maybe a dozen field RAs applied for economics PhD programs a few years ago, now it is dozens. Maybe dozens upon dozens. This is less true for political science, where the tide is surging but still low. But not for many more years.
2. Enthusiasm for RCTs is moderating. Enthusiasm is still high, and will remain high. But we’re beginning to see the warts and the limitations.
3. You might get less interaction with a professor than you think. This varies from academic to academic, and project to project. You might find yourself in daily conversation or you might find that they barely know your name. The latter is seldom the case, but that is the spectrum. If your aim is to get a good letter of recommendation, one side of that spectrum is better than the other.

Pros

1. You may never have a chance to live in a developing country again. In your PhD, you’ll be confined to a trip of a few months maximum, here and there. As a professor, you’ll reach the absurd level of visiting four African countries in 14 days. This is your only chance. And it will make a difference about the kind and quality of questions you will ask and care about.
2. You will learn hugely useful skills. I can’t speak for other professors, but my RAs learn to design questionnaires and behavioral games, do better qualitative work, code Stata, run real-world regressions and deal with real-world statistical challenges, hire and mange a team, manage and budget hundreds of thousands of dollars, work with policymakers, write for a wonkie audience and, most of all, manage harried and absent-minded professors. You will put all of these to work in any dissertation in the field.
3. You will be given room to excel. You will be more independent than you expect, which will be scary, but probably good for you. Your bosses will throw as much at you as you can handle, and then some. Over two or three years you will usually get the responsibility you deserve, which can be a lot, and take you great places.
4. You might get more chances to impress than you think. Even if you’re not on the phone every day with the professors on your project, you have many opportunities to shine, and we look out for those and they land in our letters of recommendation.
5. It will lead to research ideas. It is no coincidence that Michael Kremer’s students are mostly celebrated academics themselves now, and all run projects in Busia. Likewise you will see the same for the Duflos and Karlans of the world. And my cohort all have PhD students who are collaborators and c o-authors who are finding great dissertations in our field sites, RCT or not. It’s a good machine.
6. It’s tough to get other kinds of positions with development professors. They are there. I am sure the Besleys and Rodriks and Robinsons and Acemoglus of the world hire full time RAs, but I am not sure how many or how often or simply how. that might be telling.