... but for starting, please permit me to correct two small errors:
The UN Maxi Diver is rated to 300 meters, if I recall correctly, and the GO Evolution Sport does not come with both, the steel bracelet and the rubber strap. You have to purchase the other one extra.
Hhmmm ... it is difficult to give a good advice. Honestly, I like all three of the watches you mentioned, and I would even add another one to this list: the Chopard Deep One.
Of all these watches, the UN has the least unique movement, since it is based on the ETA 2892A2. So if a so-called in-house movement is really important to you, you have to drop the Maxi Diver. BUT: Especially for a sports watch that is exposed to more hazards than a more elegant timepiece, it is not at all wrong to use movement parts that can be repaired, or better: replaced by any well-trained watchmaker around the world. but how many watchmakers are able to repair a Girard-Perregaux cal. 33 , or a GO cal. 39 movement? They have to send it to the company, or national service center at least, since they would not get any parts, when they are not authorized dealers for the brand.
Regarding functionality, the small date windows, sunk into a deep tunnel, as offered by UN and GP are clearly inferior to the large panorama date of the GO. Also the clever micro-adjustment of the GO's steel bracelet is unique. On the other hand, the power reserve hands of the UN and the GP are horologically interesting, and give these watches a very special and unconventional appearance. The UN's small second hand further increases this effect. I would say, from the three you mentioned, the UN is the most unconventionally designed, including the dial structure and the semi-skeletonized hands.
I think the decision is likely to be based on style, and sympathy. And nobody can help you here, I fear ...
Regards,
Marcus