Muzzle loader elk, easier to draw in most units. First rifle, you can use a high power rifle, harder to draw.
Muzzle loader you are going to be hindered by the distance that you can shoot. First rifle, bang away as far as you are capable of shooting.
I actually prefer muzzle loader hunt. It is during the rut so getting close isn't as hard as it at other times. Weather is usually a lot better but as weather is it can change. I have seen a foot of snow during the muzzle loader hunts and dry as a popcorn fart the rest of the seasons in the same year.
Like Slugz, it depends on the unit. One year I drew a unit that I know has a really great population of elk. It is close to my homeplace and I scouted it all summer. I hiked many miles and saw lots of elk. I knew where I wanted to camp and left 3 days prior to the opener to get setup. When I got there, it was like an army unit had moved in. Archery hunters everywhere! I counted 10 different damps within 2 miles of where I had wanted to camp and hunt.
This is the reason I would like mz season to be stand alone and archery closed when the mz season is open.
I hunted 1st rifle last year for the first time and can second the comment about it being crazy busy. The place where we "camped" had folks lined up in tents on the verge along the side of the road all the way out of the parking area. There must have been 50 people camped that way. I talked to one old guy who had been going there for years and he said people get there literally a week ahead of time to make sure they get a good spot.
I think a lot of the crowding is going to be specific to the unit and season. Look at tag #s for elk in archery/muzzleloader and 1st rifle (deer also for muzzleloader and archery), is the area OTC in archery season, etc.
I personally would look for a unit that limits the number of archery hunters, thus not over the counter and has a decent success rate for muzzleloader season. Hunting wapiti during the rut, when they are screaming and chasing the girls around is the best.
PM me and I can help a little more. Herd size, summer concentration areas, calving areas and access points should be looked at close. I think then it may provide a clear choice. Like I said above, its a unit by unit decision.