In addition to what Kevin said you may want to find a unit to fall in with before buying anything. They usually have loaner gear and may have a preferred musket to use. It may also give you a chance to see which one you like better.
Also, IMO the 42 Springfield is the most accurate reproduction when compared to the P-53 Enfield and the 61 Springfield.
You can also visit my Show and Tell page and pick up some information on other gear.