I know for me, the minimum size per order and breeds available are important. Some if the hatcheries suggested have pretty large minimum orders. I ordered 6 this time, which is the largest number of chicks I've ever had at once. I prefer to add 2 or 3 each year to hopegully keep my egg supply going after my older chickens retire.
I've split orders before so I could meet shipping minimums and still only add a few, but I couldn't find anyone nearby to do that with this time. So I have to look for places with smaller minimums, which is why I ended up with Meyer. They have the breeds I want and ship smaller orders.