I have a bunch of IEP friends who faced the same choice last year and (as is obvious because they are in IEP), chose HGSE. Paraphrasing, I think it came down to three things for them: 1. The range and network of faculty, 2. The diversity and depth of their peers, and 3. the intellectual community/vibrancy and real world interface/connectedness of HGSE and Harvard generally.
Re (1), Fernando Reimers, Felipe Barrera-Osorio, Pasi Sahlberg, etc. all have deep networks with government and nonprofit leaders all over the world. Some of my friends are currently spending this week (spring break) in Colombia where they have met with the Vice Minister for Education (an HGSE '07 alum) and have toured various agencies and nonprofits. They are currently guests at of the Colombian First Lady at the palace in Cartagena - and the kicker is this is not unusual. Others are in China, Korea, Philippines, etc. at the moment (e.g. The Kennedy School and HGSE conduct an Asia Leadership Trek/Fellowship program three times a year for current grad students where they also interface with high level government and nonprofit leaders - google it for past trek info). Also, many leaders in the field teach at HGSE. Bruno della Chiesa from OECD taught a course during J-term and has done so for the last 5 years. I can't overemphasize how connected the faculty is to leaders all over the world.
Re (2), the IEP program is usually the second largest cohort in the master's program. This year its tied with EPM at number 2. The 65 or so folks in your cohort will come from all over the world (I think I read that Stanford's program is around 12-15 students). In this year's class (from memory), there are students from China, Malaysia, Singapore, Japan, Thailand, India, Pakistan, Jamaica, Brazil, Chile, Mexico, Peru, Argentina, Ghana, Sweden, UK and elsewhere (on top of folks in other programs from around the world - 46 countries represented and non-US students represent about 20% of the total students in the EdM program - so 120-130 international students at HGSE vs. 30-40 at Stanford). It's pretty impressive to see such geographic diversity. Also, the EPM and IEP folks also tend to interact with students at HKS as well who also hail from various places outside of the U.S. There is frequent collaboration (e.g. the Colombia trip, the Asia Trek, etc) on academic and social events.
Re (3), we often joke that Harvard is our "fifth class" - there is so much going on around campus. This past year, HKS has hosted 5 heads of state so far (I got to meet the President of the Philippines and members of his cabinet) and that's not an unusual occurrence (check out https://forum.iop.harvard.edu ) . Other parts of the university have hosted folks ranging from Ban Ki Moon, VP Joe Biden, Gov. Deval Patrick, Thomas Piketty, Peter Thiel, and Edward Snowden (via Skype) to celebrities like Oprah, Shonda Rhimes, Barbara Walters, Eva Longoria and Seth Rogen. And that was basically just first semester of this year! At the Ed school, we've had Garth Brooks, Trisha Yearwood, Claude Steele, Mark Yudof, Jose Antonio Vargas, Carmen Farina, and many more (search Youtube for HGSE Askwith Forum to see some recordings of these events). And all of these events are open to all Harvard students. Every day of every week there is something going on, and its more than I had expected even having gone to a prestigious/globally-known undergrad. It is really a special place in that way.
