Well, about your question, they are so different watches. I think it comes to what one wants but hard to find elements to compare.
Your friend has made an excellent move as it is a beautiful watch and interesting model regarding the context and colors used. He has obviously expressed his preference for the 5230G NYC and that's a great catch.
However, I personally can't compare both references you mention. Indeed, on the one hand you have an exceptional enamel work with a more classical case, on a bracelet, while on the other hand you have an engraving with a totally different "spirit", and with a crafmanship that requires quite some skills and knowhow.
In the end, the watches we enjoy are not necessarily the most expensive or the level of craftmanship. They should sing to us. Many creteria to take into account which are very personal
All depends on the level you compare. I would have maybe chosen the 5230 NYC because of budget, chance of allocation, everydaywear potential (as I use my watches over a long period). But, if craftmanship or poetry were my goal, then I would have chosen the 5131P.
As for value, as you know we won't mention this part here (as no one even know the answer) :p
Thanks a lot for sharing Gordon, much appreciated and congratulations to your friend!
Best, Mark