I assume we're talking rear discharge here. Also, I need to make a minor disclaimer. I did not have any hand in the design of the First Choice machine and manufacture and assembly are not done in Midwest's Illinois facility. So my observations are from the machines I have seen running. My comments on contruction are limited to my taking both machines completely apart and putting them back together to see how they work and are built, not from an in-plant perspective. In addition, there may have been some design changes to both units over the years, and the units I dissected may not be the same as the ones you see. That being said, here goes.
The deck on the First Choice unit looks similar to the Land Pride at first glance, but there are several differences.
Both decks are break formed. The rounded front corners are welded in on each. The difference is that the First Choice unit has the welded edges ground smooth for a cleaner look and no lip sticking up to trap grass and water. At the rear of the deck the welds on the FC are ground smooth as well. This gives the FC unit the look of a one piece stamped deck without the limitations in forming. The LP leaves the sides sticking up slightly above the deck and welds left as is. The fit and finish on both decks is very good, you just see how the LP is put together easily. The rear center of the FC is rounded rather than pointed to reduce the tendency to dig in going through dips and has skid plates built in on the sides toward the back of the machine. The material of both decks is the same other than a minor variation due to metric material being used on the FC.
The next difference is in the guage wheel mounts. At the time FC started shipping, the Land Pride used a formed channel, while the FC was formed tube. Much stronger and better looking with less corrosion, in my opinion. I've noticed new LP units have gone to tubing as well.
Perhaps the biggest mechanical difference is in the belt tensioning. The FC uses 2 matched belts tensioned by sliding the gearbox. The LP uses 1 belt with tensioning springs and idlers to accomplish enough belt wrap around the drive pulley. Seems to me that the FC is simpler with less slapping of the belts as the unit is powered up and as it encounters clumps and tougher mowing. Just watch the belts on two units with the guards removed and you can see what I'm talking about. A single belt can cause accellerated spindle and gearbox output shaft wear, since the gearbox and the center spindles are constantly loaded from only one side. Of course, everyone's outboard spindles are loaded from one side, so there's no advantage there. I know there was some discussion of gearbox failures on the early single belt LP units, but believe this is sorted out now. Maybe that's why they changed to the Sicma box this year. Now, several of you may prefer the single belt, and as I'm currently building prototypes for an American built mower, I'm certainly going to listen.
Of course, the biggest difference to the eye is the paint. Not sure what system LP uses, but it seems to chalk over very quickly vs the FC powder paint stays bright and shiny for at least the 3 years I've seen them running. Even if both machines were identical, you can spot the difference across the lot by the paint, especially on units which have been used or sitting on the lot a few weeks.
The gearboxes are different models but made by the same company. I believe both units are available with air or solid tires and have similar blade tip speeds. Both use a top clevis and floating hitch blocks for terrain compliance. Both use the same spacer gauge wheel adjustment system. Both machines have a good track record in performance and longevity.