I’m going to buy a new tractor in the spring and am pondering the same 2 machines. My uses: I mow 20 acres of native grasses with some light brush, so I need a 6’ rotary cutter. I maintain 1/2 mile of gravel road and snowplow, so I need a 7’ offset rear blade. I rototill the garden once in the spring and plow once in the fall. I use the loader to move materials and sometimes heavy hay bails for feeding. The last item moves me towards the MX, but this task is infrequent (I raise a few steers every couple of years when the freezer gets low). Also, weight is good for road maintenance. But the MX is $5k more.
Cost of the machine at 5K more seems significant at the time of purchase but 10 years down the road is a not so big of a deal.
I had a similar concern when I purchased my l3800 in 2012. I was looking at the l3800 manual trans (524 loader, bh77) vs l4600 (764 loader,bh90(OR 92) both outfitted LP rear blade, auger, 5 ft rear mower for the then 6 ac property. The primary need for the tractor was the 4 wheeler and blade couldn't keep up with our winters by February and we needed a way to push more snow effectively. We also raised some beef, prepped firewood from logs, mowing, cleared 30 years of wild rose, snow moving on a 300 yd driveway, and other typical farm chores.
There was a $9K difference in cost with the more capable loader/backhoe, bigger platform and weight. My wife insisted on paying cash and at the time I didn't understand that the added capability was worth the additional $9k for my then undetermined and seemingly small farm needs. It seems that we were able to most of our chores without a tractor, albeit with much more time and effort. The l3800 filled most of my needs, but wouldn't lift a tote of barley (1500#) pellets and move them or allow me to stack large square bales (1000#), at least directly and safely. I'd use the roll back function on the bucket (backhoe and rimguard for ballast) and have my wife drive the truck out from under the totes and then I could place them down in one spot and I would flip the bales (with bucket forks) onto each other but could never go more than 2 high.
Anyway, we now live at 42 ac mostly timbered property, take care of a 1/2 mi gravel drive, skid logs, maintain access roads, mow 7 acres of field, and clear brush (lots of wild rose and those tall southern ID variety junipers). That $9K difference would have made a big difference in ability to lift more material/weight and the weight associated ground pressure needed to skid some of the longer logs I have tried to move without having to cut them down in size. The heavier ground pressure would be useful with the wicked 55 root rake for wild rose and other brush. It works pretty good on the l3800 in the wet spring ground but not so much in the summer. There are even times when the bigger machine would have helped w plowing snow.
If I had purchased the L4600 I probably wouldn't be in the market for a bigger machine. $9000 more doesn't seem so significant 10 years later. If you can afford, want, and can use a bigger machine then I'd recommend getting one (as I'm sure others would too).