Energy generation is what you want for cloaking. It is fine for the job too if you know how to build it right, even if you typically need to go bare-bones for such designs. Cloak and jam energy costs are steep, but that is fine until they better balance them anyway.
Energy CAPACITY, which you get from tanks, is meant for larger ships. The ones that have weapons that would drain the default 20k in a single shot (if not require MORE then that to even fire their biggest guns).
It is exponential. The tanks give only a little bit at first. Keep adding more that are connected, and capacity will start rising faster and faster with each one you add. Eventually, you will get to the point where each additional block added easily adds hundreds, then thousands, and even more energy capacity. Ships that actually need that much more capacity can easily fit it in too.
The only reason currently to use them with a cloaking vessel is because servers may have issues with keeping your cloak and jamming up (i.e. any lag burst will cause your cloak and/or jammer to turn off, and having extra capacity will help reduce this with a larger cloak-capable ship). A smaller cloaking vessel of course uses less energy a second and is less prone to the issue anyway.
Then again, theoretically, you could build a large vessel centered around cloaking and jamming that uses a downright MASSIVE number of capacity tanks, unless there is an eventual cap on the limits of capacity. While generation has diminishing returns, tanks are the opposite after all, and as you add more the added effect INCREASES per block. So you could supposedly use that to make a very large ship that can stealth for a reasonable amount of time, even if it needs to recharge for a few minutes between uses.