What manufacturer would you recommend for a HO code 83 #6 switch?
Peco or Shinohara.
Atlas
I would choose Walthers/Shinohara as best value for money over Peco or Atlas. Atlas because of the ugly frog and Peco because of price. Peco does have the overcentre spring to locate switch rails which can be an advantage in some cases
What are you using to throw the turnouts on your layout - Tortoises, twin-coils or manual throws?
tortoises for main line and yards, hand throws for everything else
For a ready made #6 turnout - Walthers or Micro Engineering. If you want to test you skills try the CVT turnout kits. Lots of detail can be added to them for a more realistic look.
jktrains.
You probably don’t want to use Peco turnouts with Tortoises. If you do, you need to remove the spring from the turnout. It will work if you do that, but it’s an extra step.
I don’t know about hand throws. I suspect that the spring would be a real plus here, because it holds the points solidly against the rails. You may not like the “snap-over” effect when operating the hand-throws, though.
I use Peco turnouts with the Peco twin-coil motors. I’ve been very happy with that combination. I’m also using Atlas turnouts with their twin-coils, and I have no technical problems with them. (I just hate the way they look.)
Before i started building my new layout, i bought a Walthers #6 and a Peco #6 for comparative purposes. Although they are both described as code 83, the walthers uses a slightly bigger rail section than Peco, just something to be aware of. I also found that with RMA standard RP25 wheel sets, there is a slight lateral drop of the wheel between the frog nose and the wing rails. This was less noticable with the Peco turnout.
In the end i used all Peco electrofrog with the springs removed and Tortoise machines.