It’s my experience that cold-conditioning in a secondary fermentation vessel gives me a cleaner beer, and faster. When I bottle, there is a huge difference in the amount of yeast sediment in the bottle when doing secondary vs not, but of course this depends to some extent on how flocculent the yeast is and how long it’s in the primary.
Anytime you transfer, there will be a certain amount of sediment that makes it from one vessel to the next, and if you assume that this amount is a percentage that’s reasonably consistent, the above makes perfect sense.
As far as the risks of a secondary, they certainly do exist if you’re not careful. Personally, I worry about oxidation from the transfer process more than infection at that stage of the game, but either is possible depending on how you go about your work.
There are lots of folks who don’t secondary, and I’m sure their beers can be great. I would recommend that you compare the results vs. a longer primary for yourself and see how much difference it makes to your palate. Might be a bit difficult to do unless you do the comparison between identical or very similar beers, but if you can’t perceive a qualitative difference, there’s certainly no reason for the added risk and work.