Once again, the size of the tank is not what's important! There will be exactly no noticeable difference between the performance of a 60 gallon tank and an 80 gallon and the slight differences there are does NOT translate to better performance! This has been covered a couple of dozen times at least and a quick search will bring up tons of info on selecting a compressor but buying one based on the size of the tank is a big mistake. CFM is what matters so base the selection of the compressor on the CFM performance vs the projected CFM requirements. Basically when selecting a compressor the buyer should consider the SCFM rating, duty cycle and overall quality vs the amount of money he can spend, the size of the tank (within reason) simply does not matter- a big tank does NOT MAKE A BIG COMPRESSOR!!!
The difference in run time between a 60 gallon tank and an 80 gallon when using air hungry tools like paint guns is mere seconds and then even that is lost to the proportionally longer recharge time, nothing is gained. Over any given work period the run time vs the recharge times will be exactly the same regardless of the size of the tank so it is and always will be a trade off. Larger tanks are used with higher CFM compressors to balance the run vs recharge times and do NOT increase the performance, that is not and never was their purpose. The problem is that compressor manufacturers are well aware that some people will run straight to the biggest tank in the store because a huge tanks just look big and bad so the cheaper outfits mount small under powered compressors on uselessly over-sized tanks to dupe the buyer into thinking he is getting more compressor than he really is, a tank can not put out more air than the pump puts in! If a 60 gallon tank is running out of air at an annoying rate at a certain rate of usage then just how long would it take to run out if the tank was only 20 gallons? Obviously it would be a short time indeed but that's all the extra run time that would be gained between 80 vs 60 gallons and then even that will be lost to the longer recharge time so NOTHING is gained. Buy CFM and quality and don't worry about the tank, the tank will be sized according to the pump and motor by the manufacturer.