With ferric chloride, the chemistry is the same whether you start with crystals or liquid. Price would be my guideline. Ferric chloride solution is used in water treatment plants. It is probably quite cheap in bulk. I prefer the dry chunks (hexahydrate) to make my solution; others use the anhydrous powder. Whatever route you go, calculate your cost per gram of ferric chloride (FeCl3).
As an alternative, you might want to consider cupric chloride -- Cu(II)Cl2. It can be prepared from the oxide and hydrochloric acid (HCl). The product from etching is copper (I) chloride, which can be re-oxidized to cupric. You need to replenish the HCl from time to time, but it is a perpetual etching bath. I switched to copper chloride a couple of years ago. I have found it to be convenient, but a little more touchy for timing than ferric chloride.
John
Here's a nice link to the copper chloride method: **broken link removed**