Originally Posted by Cape Brewing
I don't think it is a matter of any of the ports making the pots "better" or "worse"... it is simply a matter what how exactly you are going to use the pot and therefore how many ports you require. You need to think through your set-up, figure out how many ports you need and simply pick one that best suits you.
For the brew kettle, the extra ports are not so much all-grain vs. extract but what features you want - which could apply to both. You'll need at least the one port to drain the wort. A second port for a thermometer is nice if you have an immersion chiller so you know when to stop chilling - maybe less important if you're going to go with a plate or counterflow chiller. A third port could be for a sight glass. My current kettle has a sight glass and it is nice, but a plastic spoon with gallon marks worked just fine for a number of years.
IMO these features are actually less important than deciding on size. If you are sticking to 5-8 gallon all grain batches then a 15g kettle sounds good. I do 10g all grain and I am really glad I went with the 20g kettle. I know plenty of folks do fine with 10g batches and 15 gal kettles. I frequently do bigger beers that start with 14-14.5 gallon boils, seems really tough in a 15 gal pot.
hope that helps