So far (even tho I’ve purchased 1/8" bits from Ryan) 1/4" 2 flute upcut spirals is all i’ve used. I was getting the diablo ones from Home Depot, but now I get the Bosch ones from Lowe’s and they seem to last longer.
On that note, I’ve mostly been cutting bigger stuff in 3/4" so the length needed to be there, and only the 1/4" give me that depth. I do have a 1/8" Bosch 2 flute upcut bit, that is 1/4" shank when I need to do smaller stuff. One day I’m going to finally break open all the bits I got from Ryan and give them a shot. I just haven’t been cutting alot since our world got turned upside down. sigh