Ghost ring sights:
Advantages- Probably the best, IMHO, overall sight for its versatility when needing a sighting setup useable at both close and long ranges, easy to adjust, allows for quick target/front sight acquisition due to its relatively unobtrusive and generally forgiving rear sight aperature.
Disadvantages: Can become somewhat tough to manage a consistent POA/POI when used for long range shooting (at small targets) as it can be difficult to keep the front sight from "drifting" around inside the large rear sight aperature, since its a front/rear sight setup there is a bit more hardware getting in the way when dealing with "how do you do" distances regarding HD, more difficult/time consuming to replace, needs adjustment at times.
Tritium sights (Im assuming you mean tritium front bead):
Advantages: Great for close distances as there is much less hardware getting in the way which may hinder front sight "focus," ideal for HD ranges, easy to replace, does not (I believe) require any adjustment if initially installed correctly, inexpensive to replace.
Disadvantages: Cannot truly be adjusted to any appreciable degree due to its static nature, not very versatile thus limiting its usefulness to close ranges (medium range at best) unless one has sufficiently practiced using such a setup.
I could probably come up with several more thoughts regarding these two sighting devices, but those listed are the first thoughts that came to me. Keep in mind, my response is by no means "the final word" as I do not claim to be an expert in such matters. My thoughts about this are merely based on my own personal experience/preferences. Take from them what you will.
To sum up, I prefer a tritium front bead sight when it comes to HD due to its simplicity, quick acquisition and thanks to the tritium feature, its ability to function as an effective aiming "device" at night. In regards to the GR sights, I tend to prefer these for shooting slugs at medium to long ranges as they allow for good target acquisition, are easy to "see" and are easily adjusted.