The difference will be the price of the system- it is higher at HD. The replacement filters are also priced higher there.
You would want a 4 or 5 stage system for your tank as that will help all of the cartridges (and membrane - the expensive one to replace) last a lot longer.
Many of the ones our site vendors sell can also be used for drinking water (never use a DI cartridge if you are planning to drink the water) and come with the faucet adapter and/or a small storage tank to store the drinking water.
The quality of the systems, and for the filters, sold into this hobby by reputable vendors is better than you'll find in a drinking water system at the hardware store.
Additionally - the hardware store systems are RO's, not RO/DI's.