I once had 38 in-line muzzleloaders in my basement, did extensive reviews and testing for a book on the in-line. Considerations are accuracy, simplicity and quality when looking at muzzleloaders. The fewer parts the better since there is a lot of combustion residue to deal with. Smokeless has less residue and it is non-caustic which is obviously why many guys like it. With most charges the actual velocities attainable are not much different between smokeless and black powder substitutes. One consideration might be that with one simple wording change, the use of smokeless powder in muzzleloaders can be outlawed very easily (no nitro-celulose) if legislatures decide they are too far from the original concept of muzzleloading.
.. hard to beat pellets for consistency, accuracy and ease of loading
.. loose powder (BP, substitutes or smokeless) require a measuring device, not so with pellets
.. smokeless requires a powder scale and speed loaders, not as simple as dropping two or three pellets down the bore
.. rule of thumb, U.S. made barrels are usually more consistent than off-shore barrels. Off-shore barrels can shoot great, but more loose/tight dimesions in bores than T/C or Green Mtn (Knight) barrels.
T/C Omega and Encore are the leaders right now, being copied by others big time. Knight's new rifles are not like we used to get from Knight when they lead the field. Disc rifles are getting pretty long in the tooth.
New stuff to come, might be wise to wait a while before making decision - trust me, worth waiting a while.