International Relations graduate here!
Human Geography and International Relations are not necessarily alike. They have a few points in common, but they are quite different at their core. A Human Geography course is basically a Geography course without the physical aspect (maps, geophysics, etc) while an International Relations degree is basically a Politics course that focuses on the global rather than national side of things.
Judging from what I have read about Human Geography, they focus way more on the environment, sustainability and geographical considerations (such as food security) in relation to how they affect people. For example, 'How does migration affect culture and development?' would be a human geography question. Pretty much everything you imagine when you think of 'green politics' falls under human geography, though it is present in International Relations or Politics courses too. In practice, that means you would have more modules touching upon those topics if you study Human Geography.
On the other hand, International Relations only concerns itself with the political side of things. In other words, how do things impact how countries interact with one another? Those things can include, but are not limited to topics like national politics, foreign policy, culture, geopolitics, the environment, conflict, the economy, development, international institutions and so forth. Naturally, that means the amount of modules you will be able to take about stuff like the environment is potentially smaller depending on what optional modules are offered, though you would gain a more complete picture of politics on the global scene.
Both globalisation and NGOs feature in Human Geography and International Relations degrees, but the way they deal with them is relatively different. As an International Relations graduate, I would ponder on how those two affect relations between countries and other political actors (e.g. pressure groups, international organisations), the global political climate, conflict, international trade and international development. A Human Geography student would probably look out for how globalisation and NGOs are impacted by human geography factors (migration, development and so on), as well as for how globalisation and NGOs can play a part in changing the face of human geography (like demographics) as we know it.
It is worth noting that Human Geography degrees have fieldwork incorporated into the assessment (check the course structure in case you are not sure if the universities you wish to apply to have fieldwork) while International Relations degrees do not.
In terms of employability, the kind of jobs you can do with those degrees differs slightly. For example, you would be more likely to find a Human Geography graduate in a position dealing with environmental factors while an International Relations graduate would be more likely to be found in diplomacy. That being said, both degrees can lead to literally the same careers, so it does not mean that you will be excluded from certain careers if you pursue one or the other. Personally, I think International Relations is a bit more employable purely because it is broader while Human Geography is just one area of geography/geopolitics. Even so, if you already know you definitely want to go into a certain area of International Relations that is better covered by Human Geography, go for it!
However, it all depends on what you want to do long-term. In my case, I want to work in diplomacy, an international organisation, the civil service, conflict mitigation or international security in the future. Those areas are much better integrated in an International Relations degree than in a Human Geography one (there is some overlap, though). If one wanted to work as, say, an Environmental Affairs Officer the United Nations, both degrees would be acceptable, but a Human Geography one would be slightly more related to that than International Relations.
When it comes to reputation, Human Geography is definitely a much more uncommon course than International Relations, so International Relations could be argued to be more reputable, though the subject you study does not actually matter that much in the workplace. I cannot remember the exact number off the top of my head, but I have seen a study which showed under 20% of employers care what degree you study. Do not think much of reputation, both of them are acceptable degrees.
In summary, it all comes down to what you are interested in most. If you are more interested in how things affect global affairs, go for International Relations. If you care more about geographical factors and their impact on people, go for Human Geography. But before you do that, make sure you check the course structure so as to ensure that you are embarking on a course you will genuinely enjoy!
At the end of the day, what you study does not matter as long as you can prove you have the necessary skills for the job. What employers look out for more so than what you study is transferable skills (communication, teamwork, etc) and work experience. My best advice to you as a recent graduate is to choose which degree interests you most and to gain as much relevant voluntary or paid experience during your degree as you can.
Feel free to ask me anything else, I would be more than glad to help since I have actually studied one of the degrees you are considering