I use a 60 gallon fimco my dad bought and used once or twice, then let it sit for several years. I had to buy a new pump, then rebuilt the old pump. Works fine for me, but I've done a lot of modifications to the plumbing with quick connect banjo fittings and valves so I can disconnect the pump and hook it up separate from the sprayer (or change the pump quicker if one stops working), oil/flush the pump without contaminating the tank, and clean the tank quicker without recirculating what I just washed out. I just recently added a water hook-up so that I can fill it up through the return line instead of filling from the top which causes foaming once the chemical is in there.
Whatever you get make sure you flush the tank and all lines well and put oil in the pump to keep it from rusting.