Here is my opinion, I bought a ten gallon Polarware pot with no valves. Took it to a welder who screwed it up. Fixed the best I could, and used it for a few batches. Figured out that it takes the same amount of time to brew 10 gallons as it does 5. In order to brew a 5 gallon batch you will sometimes need 7.5 gallons in the kettle. This leaves you a real problem with boil over. There isn't much price difference between 10 and 15 gallon pots. I would get the 15 gallon pot with dual couplings installed, if possible. The reason being you may expand down the road and may want to use it as a mash tun or HLT for larger batches. My 10 gallon pot now is my hop back, decoc pot, pilot 5 gallon batch HLT. GO 15, you will thank me down the road. I would also look for a pot that is more tall than wide. This will help with having less boil off. If you find one w/o the couplings it isn't hard to find a welder to install a few 1/2" couplings. Sorry for the long winded answer, just my $.02.
