I bought an all copper bar still to do my testing on, for the same money as an air still you can get a little 5lt elephant trunk still or similar online.
Mine was stupidly expensive but when it's clean and shiny it's a great decorative piece, but running on an alcohol burner it it gets very dirty.
But I get one 750ml bottle of drinking spirits per run so it's perfect for experiments without investing a heap in mash ingredients.
My favourites have been quince, tequila from pure blue agave nectar, whey from non homogenised milk and coffee.
They are great to have as you can have a fully functional display piece.
But I have used an air still a lot, no mess, easy to operate and quick to clean.
But it's hard to get the true potential of a mash from one without doing 3 striping runs and a spirit run.
But you can still get an idea of what the taste will be from one, and if it tastes, good then you know it's a winning mash to go full scale on.
Excuse its messy state, I've done a few runs this week on it and it's been worked like an illegal immigrant this past couple of weeks.
It's going to get the vinegar and tomato past clean this weekend to make it all shiny again, well until the sorghum and rye whiskey batches are ready to run anyway.