Hay should be the first ingredient. Whether alfalfa or a grass hay, depends on the age of the rabbit and whether it's a pet, nursing doe, etc, because of different calcium levels and protein levels.
If this is manna pro you're talking about, the basic ingredients are similar, but oxbow is the better of the two in my opinion, the main differences being the fiber percentage and the better quality control.
High fiber, balanced with the right amount of protein/nutrients, is considered important for optimal digestive health in rabbits. The lower percentage of fiber in the manna pro pellets could be offset to some extent, with free feeding good grass hay and limiting pellet amounts, if the quality was as good as oxbow, which I don't feel it is. This is based on personal accounts I've read from others, as well as my own experience.
I don't know if the select series pellets has better quality control in the ingredient and pelleting process, over their farm store bulk rabbit food, but having used both oxbow and their show food, I've seen for myself the effect on my own rabbits. Trying to switch from oxbow to manna pro show, to try and save money, I saw a change in my rabbits poop becoming mushy and unhealthy looking during the gradual transition process. No other changes were made in their diet that could have been the cause, other than the change of pellets. Same hay and greens as before.
Now I'm extremely careful with my rabbits diet due to some having been prone to digestive issues. I had 7 rabbits at the time and the manna pro affected all of them, showing up in negative changes with their poop, which is a reflection of poor digestive function and health. So I transitioned them back onto the oxbow and their poop went back to normal. Which leads me to believe that the difference in the pellets had to come down to the quality of ingredients being used or something wrong in the process in making the pellets.
I've tried many different pellet brands over the years, and the ones that I more consistently had problems with in quality and it's effect on digestive health, was always with the lower quality bulk feed store pellets brands. This would include the Walmart food.
Nutrition of Rabbits - Exotic and Laboratory Animals - Merck Veterinary Manual
https://wabbitwiki.com/wiki/Nutrition_for_rabbits