In my personal opinion, the most important criteria when deciding what sort of organisation to work for are:
1. Career opportuninies - I think that an opportunity to grow and develop is crucial in work. I don't see myself being satisfied with staying on the same position and doing the same tasks for years. I would highly appreciate having a path that I could follow, offering me new challenges and chances to go out of my comfort zone.
2. Training and development - This would make climbing the company's ladder possible. Learning and acquiring new skills causes growth and I would highly appreciate employer's help, motivation and belief in me.
3. Ethics - I would have to consider the company's ethics, because all the development opportunities or even money would not mean much to me if working in said enterprise was not coherent with my views.
The criterium I would consider the least is Alumni programme. I don't think it's unnecessary, because I see how it could be very helpful in a situation of exemption or quitting work. However, it wouldn't have a big influence on my decision. I would manage with or without it.