This is just observation ,not scientific but I just finished getting a CA95 running again that I bought last year . This bike needed a replacement wiring harness along with replacement coil ,rectifier . The rectifier I used was an old one I had and reused on this bike .
Checking the charging system once I got the bike running the rectifier was marginally charging the battery . I purchased a Radio Shack rectifier and from went 6.3 charging volts to the battery to 6.5 volts with the Radio Shack rectifier . I then replaced the RS rectifier with a unit I purchased from Oregoncycle and I now have a charging voltage of 6.8 volts to the battery.
This was at a high idle maybe 2 thousand rpm . No I didn't check voltages at higher rpm or lights on honking the horn but almost .5 volt higher over the stock regulator . I saw similar results when I replaced the rectifier on my red bike . The Oregoncycle rectifier seems to perform better than stock or the Radio Shack rectifier . To me $22 well spent
Rectifiers
I've used Oregon Motorcycle Parts for 3 restorations now. Prices are low and the service is great. I've never retained the original selenium rectifiers. Selenium degrades with time, so even 40 year old, unused NOS rectifiers off the shelf won't be as efficient as when they were new. Silicon is the way to go, especially for those of us that have retained the 6-volt systems. There's not much room to lose any efficiency with 6 volts.
http://www.oregonmotorcycleparts.com/rectifiers.html
http://www.oregonmotorcycleparts.com/rectifiers.html