Ive been swapping back and forth between the Nitto cruiser and moustache bars and have concluded the following:
The cruiser bars are probably the most comfortable ones Ive ever had. However, I certainly dont feel as connected to the bike using them and steering feels quite vague. The difference in air resistance whilst peddling against wind (which is common when you live by the sea) is noticeable and more tiring. I think that they suit really low gearing - around 55" as a top gear on the SA3. They make the Guvnor look like a traditional roadster - a little like a Sovereign with the mudguards and chain case removed. Whether this is a good or bad thing is down to individual taste I guess.
The moustache bars make me feel like I am sitting in the bike, the steering feels more direct and against the wind or downhill there is way less air resistance. Combined with the short reach stem I dont feel too hunched over or stretched out. Climbing hills feels easier. Higher gearing feels better which for me is a 63" top gear. I think that they look great and are in keeping with the path racer aesthetic.
They are both great bars in my opinion and a big improvement on the standard ones. The moustache is my current favourite.
Just to add - I suspect that I am in a minority as regards the original leather handlebar grips. I really dont like them, they feel too big and clunky to me though I do admit they look nice. I much prefer the vintage style (and way cheaper!) rubber grips shown below.