These are molded adapter cables. Not much can go wrong with them. It's not like you were looking to make one yourself.
I didn't even think about going with 110/120v when it came to making the jump to electric. I do wish I had gone with the panel I have on order the first time. Actually, no, I don't because they've made improvements over the previous design that I can take advantage of. I did get a sparky to provide me the correct outlet (14-50) in the garage to run the power to the panel. I've already run a cable from that to where I'll connect to the panel (when brewing outside at least). IF I need to, I can get a longer cable to go from the panel to the extension (panel comes with a 6' cable, I've already seen 10' versions). I'm just hoping I won't need to. I'm also getting ready for brewing in the winter where I'll be setting up in the garage (warmer weather is in the driveway, under a canopy). We might even do some batches in the garage before winter. Basically, the weather really won't be a factor moving forward.
Generally speaking, if something can run on either 110/120v or 220/240v it will use the same amount of watts. Which means under 220/240v it will pull less amps from the panel. For things like motors you can run cooler due to this. I'm sure something similar happens inside the control panels. Either for the SSR or some other components will run cooler than trying to do the same with the lower voltage.
Depending on where you are, as well, you probably have 240v at the outlet. I know I have the three 240v outlets in the garage (now). Basically, the 5500w elements are pulling less amps to make power than if I was using 220v or something other than 240v. Typically, in the US, residential power is 120v/240v. A lot of people just call it 110v/220v. Commerical (three phase) is a different story.
