My ultimate muzzle loader may be different from yours.
Some get into muzzle loading for the nostalgia and tradition. An original, replica flint or cap lock would suit them.
Some get into it so as to capitalize on hunting seasons and areas, for them an in line or break action is where its at.
For others its versatility, any shot/ball/bullet combo with various powder charges.
For me its heritage,and versatility along with a hands on feel of satisfaction you get from building your own. Nothing makes you more proud than taking home game that you bagged with equipment you made yourself.
Where are you at?