I am asking all your opinion on what a good brand of flash hole deburring tool is. Suggestions??

I only have one to debur the inside. I think it is made by RCBS, but it works fine. I do not dress the pockets for hunting loads. Kudude

Got a Sinclair for 20 cal and a Lyman for everything else - both work fine.

very happy with my RCBS

I like the Sinclair because it has a "stopper" flange down at the cutter end to prevent over cutting the flash hole. It cuts until this flange touches the bottom inside of the case head regardless of case length.

I have the Lyman and RCBS tools and they work good , but they need to be feed cartridge cases that are all the same length or else the shorter cases will allow the cutter to dig deeper into the inside of the case head and a shallow cut for the long cases.
I found the lyman tool to be the hardest to set up because of the tapered stopper that inserts into the case mouth. I used 2 small pieces of 24 lb printer paper cut to paper match size and laid against either side of the lymans tapered stopper to act as spacers to set up the depth of the cut.
The RCBS tool can use spark plug feeler gauges between the stopper and the case mouth to set up the depth of cut.
All 3 tools work good, just the Sinclair takes less fiddling.

Where do you get the sinclair tool? Are they the only one makes one for 20 cal? I need one for 204 and can't find one. Thanks

www.sinclairintl.com

Search for tool DB-1255 to see what it looks like.
The shaft diameter on mine measures .219" so I don't think it will fit down a 204 Ruger case.
You might be better off with a piloted flash hole tool number 26-1000 just add the #26-xxx pilot stops for 204 cal.