Not being familiar with RDS on a pistol, I have a couple questions.
How often do you need to clean the lens of dust and debris?
I will caveat this by saying I've been running MRDS for about 12 years now on handguns.
Some MRDS on the market I believe are totally unsuitable for pistol usage.
Depends on conditions. Patrol duty - not significantly often - but water, dust etc won't really affect it (depending on model).
Does it turn on/off? Have adjustable brightness? Does this require a tool or is it done by hand?
There are a lot of different sights with different options on that -- nearly all have adjustable brightness - adjustable by hand.
I have 3 guns with Leupold Delta Point Pro's (DPP) on them, 1 with a Trijicon RMR, and one with an earlier Leupold DeltaPoint.
I plan on getting an Aimpoint ACRO P2 for a Glock 19 shortly.
But at this point would default to the Leupold DPP for anything I was going to use in a "work" environment.
How long do batteries last? Do you have to remove it to change them?
The DPP has a waterproof lid that you need to unclip - then you can change the batteries - all the other options need the sight to be removed from the weapon (a no go to me). I switch batteries on my carry gun every month at the 1st of the month, I also do the same with the weapon light batteries.
How often does it need to be resighted?
Depends on model, I picked the DPP because I had inside knowledge of a program somewhere - I haven't had any issues with it - from being jumped (albeit not a static line), rappelling, explosive breaching and a few courses, and duty use when I did that sort of stuff.
I do have cowitnessed iron sights - something I think is a must on a Duty gun. I had some bad CR2032's once - and had the dot die during the Pistol Stress stage at the 2016 USASOC Sniper Comp and had to shoot the remainder of the stage with the irons.
As attractive as they may seem, I fear a lack of basic firearms competency and maintenance puts a pistol RDS out of reach for your average police officer. I guess Vancouver will find out, as will the RCMP if this RFI goes the way its written.
Honestly pretty much every entity that has gone forward with it has seen a remarkable uptick in shooting scores - both in training and on the street. Moving and target moving, and low light engagements are significantly easier IMHO.
When running NOD's you can just use the Dot and don't need any active light source.
Now - some entities have opted for comped guns to help flatten the recoil for dot tracking and faster follow up shots - not exactly what you want for a primary duty gun - but makes sense if you are a carbine armed entity running a secondary.
A Comped Glock 19 fits in a Glock 17 holster...