Michael,
Either the 1.5 l or the 4.5 with the insert that
www.thermalcookware offers.
Amazon, Forum Appliances, etc do not offer the inserts or any other accessories for the cookers. The only seller that does is
www.thermalcookware.com that I am aware of. The accessories will make anyone's cooker much more versatile.
The 1.5 l is great for soups, stews, chili and the like. It has a tall narrow shape liike a quart mason jar. You would not be able to brown a chicken breast for example.
The 4.5 with the inserts is would enable you to place boiling water in the bottom of the larger inner pot, then brown your meat, etc in the smaller insert and place it on top of the larger inner pot. As I stated in an earlier post, the cooker must be at least 80% full to retain the thermal mass effectively.These accessories would enable you to cook whole pieces of meat, a small corned beef, small roast, etc in the smaller inner insert. This woul keep you from eating the same dish for the next 3 days or so. Of course you could cook a smaller amount of beans, soups stew, etc by putting boiling water in the large inner pot and your meal in the smaller insert pot also.With the pudding tin you could bake a cake or quick bread such as cornbread, in the large inner pot and cook another dish in the smaller insert on top simultaneously. When you have company, attend a potluck , etc you could use the full 4.5 litre capacity.
So, depending on what you want to cook either the 1.5 l or the 4.5 with the inserts. IMHO, I think you would gain more cooking abilities with the 4.5 plus the inserts.
Also, remember that when you are boondocking the boiling water that will be placed in the large inner pot will not be wasted. It can be used to wash dishes with after your meal.
I have found that the more I use it the more I like it. Also, the more I use it makes me realize that I can do alot more with it than I realized at the time of purchase.
Hope this helps. Michelle