I own early examples of both pistols.
The silver (flash chromed) hammer and trigger indicate early production, and forged parts on the 5906.
The "hollow" hammer spur on a 910 indicates late production. The later production pistols incorporate MIM parts, EDM rifling ect.
My 910 has thousands of rounds through it. It is not a bullseye pistol, but is combat accurate, and bet your life reliable. I carried it at a former agency for a few years, when we were forced to go to semi autos. Great pistol. IMHO, I would look for used. The 910 is not worth the current asking price for new. It is a superb $350 to $375 pistol, and a good $400 to $425 pistol. I would not pay more for one, regardless of how much I like them. I did swap out the 910's plastic guide rod for a 5906 metal guide rod. That tightened up the groups.
The 5906 I own has been very reliable and is slightly more accurate than my 910. It is also heavy. Nothing a good belt and holster can't overcome, but heavy enough that I don't carry it on the job.
I found a 6904 slide, and mounted it on the 5906 frame. A homemade, two tone 5906 SSV. I really enjoy shooting that pistol. Hope this helps. Regards 18DAI.