Musket caps all the way, all I use on all my sidelocks, I use the 'top hat' style and give em a little pinch around the top rim to keep em snug on the nipple while hunting.
That being said a good magnum cap will/is more weather/water proof, the musket caps are slitted along the sides and can let in moisture on rainy hunts, I have used a bit of boore butter around the circumference of the musket caps to keep moisture out while afield.
