I would pick the 30-30 hands down. Let me see, one of the most proven deer cartridges on this continent or a muzzle loader shooting pistol bullets in a plastic sleeve to make them work. A tool made for the job, or a tool adapted to get the job done?

On paper the muzzle loader looks good, especially when you look at energy figures. With a 300 grn bullet it holds energy out to 200 yards better than the 150 grn 30-30 bullet because of the weight. However the drop is twice as much at that distance.

The other thing to consider is that at longer distances the 30-30 is probably going to have more consistent accuracy than most muzzle loaders. Muzzle loaders are a lot like modern shotgun slugs, they tend to loose stability past 150 yards or so and accuracy falls off. I bet most 30-30's with the right bullets can hold pretty decent groups at 200 yards with a scope and a decent shooter. With a muzzle loader it is going to take some work to get that kind of accuracy, if you can do it at all in some cases. And I doubt it will be as consistent because of the materials used and the loading method.

And then there is the ease of use, quick follow up shot and dependability issues to look at. Modern muzzle loaders are a lot more dependable than they used to be, but lets be honest they are not a centerfire rifle.

I honestly think a muzzle loader is cheaper to shoot though once you have everything for it. Unless you are handloading for the 30-30. It's waaaaaaay cheaper than a slug gun with sabots.

My opinions anyway.

Paul