I have both an MX5800 HST and an
L6060 HSTC. Both are great tractors and have their strengths & weaknesses but I wouldn't be without either one. Based on my experience, this is all I can add to the good info already posted here.
I looked at the M series before buying and the added HP would have been nice but I'm too addicted to the advantages of the HST trans. I do a lot of loader work with bucket & forks in tight spaces and the HST is a real time saver.
Without doubt, the MX is a slightly "stronger" machine. The LA1065 FEL will lift a bit more than the LA1055 on the
L6060 and I use it for all my earthwork. I much prefer the "iron on iron" feel of the LA1065 joystick. The cable actuated LA1055 does not have a positive feel, likely due to a minute amount of cable stretch. I find it more difficult to feather than the LA1065. I complained to the dealer about it but they claim this is normal. They checked over the mechanism and it's up to spec.
The
L6060 is a heavier machine but it doesn't have the raw pulling power of the MX. (R14's on both) I don't know for sure but it may have something to do with the larger front tires on the MX. I have a BH92 hoe which I use on both tractors and, for some reason, the hoe throws around the
L6060 more than the MX even though the
L6060 is heavier. Weird.
To me, the HST+ transmission on the
L6060 alone makes it worth the extra $$. It's like having 6 gear ranges instead of 3. I can leave the trans in high gear most of the time and just switch on the fly between H and L range on slopes. I have to stop and drop a gear on the MX. The air ride seat, auto throttle advance, stall guard, inteli panel and other doo dads are just icing on the cake. I use the cabbed
L6060 for inclement weather work like plowing in zero degree temps and mowing when it's 90+. The MX gets the nod for everything else.
I also prefer the old style treddle on the MX over the newer design on the
L6060. This is a minor issue though and just requires some adjustment to my operating style when I use either machine.
Keep in mind these are just my observations based on the way I use the tractors and my personal preferences. Others may use their machines differently and will likely have other opinions.