Hi Theodore,
That is a tough question.

I would have to say that it depends on how much space you have in your kitchen and how much flexibility you want with quantities and recipes.

If you have enough space for the 6 quart Instant Pot, personally, I think I would go for that. I say this because that leaves you enough flexibility to make both larger and smaller meals. For example, if you want to make a large batch of something and then freeze the leftovers for later.

The 6 quart size is also nice because many Instant Pot accessories are made to fit in the larger pot. Steamer inserts, cake pans, egg holders, etc. Also, if you use a second pot inside the first one the 6 quart will be more roomy.

Some recipes, even have you making a whole, one pot meal – putting the meat in the bottom and placing another pan on a trivet over top the food in the bottom to cook the side dishes. I have not tried this type of cooking – but have seen it done online and again it seems that a larger size Instant Pot would make sense.

However, if you are just cooking simple recipes for one or two, the three quart size should accommodate much of what you make on a daily basis.

So, in summary – I like the 6 quart for the flexibility that it offers, but the 3 quart takes up less physical space and should work for smaller portions.

I hope that helps you with your decision.