Building single tier with sanke kegs. Already started building and "acquired" 3-3/8" ball valves to use. Noticed that most are using 1/2".....problem. Hope not as I am nearly finished with the mash tun and kettle.
I was able to get a killer deal on 3/4"ID silicone tubing and ball valves so I use that size. I have a single tier and haven't had any serious problems yet. Sure, I have had to purchase some reducers to fit pump connections but other than that it's been great.
They are fine... I run all 3/8 tubing. No problems even with 60% wheat beers. The mash tun false bottom or screen or whatever you have determines whether there is stuck mash issues--not the ball valves or the tubing.
when in doubt, just run a thinner mash or use rice hulls... but 1/2 inch valves won't stop any stuck mash that was going to occur anyway.
3/8 valves and 3/8 tubing is plenty fast... and the 3/8 inch tubing slips on snug to 1/2 barbs with no need for hose clamps... that is what I like.
If you need more speed--I don't see why you would--use half inch barbs and tubing with hose clamps if need be...
No gummy silicone messes, cleans easy, lasts forever, clear, snug on 1/2 barb easy with no clamp, hi temp, and cheaper. I use it for racking as well. The only hose you need aside from your kegerator's needs.