GF GMT is a huge watch as with most GF watches. I have tried on the GMT on the wrist and its craftmanship is superb. The GMT function is more advanced than all other GMT watches I have seen, and it allows for daylight savings time compensation. It would be a great watch to wear occasionally, but not something I would wear regularly. The 5531, having only seen in photos, look more like a wearable watch, at least compared to the GF GMT. As with all enamel dial Pateks, the dial is surely a work of art and the MR part second to none. Tough decision, but hope you get the one that you truly love!