1. Durability
Well, thats perhaps is more speculation on your part, my local dealers would argue with you to a considerable degree about the durability issue. The hydrostatics have been found to be very durable. I certainly inquired about this prior to even considering a hydrostatic. Secondly, they really are not more expensive to replace then both the clutch and dual clutch packs on todays shuttle tractors. Two Kubota dealers in my area have not replaced a HST yet so a definitve cost had not been established. He did say that they do not rebuild the unit, they would get a new unit from the factory. His estimate for the new unit was about $2500. Our new hydraulic dual clutch pack in a NH 2120 was $3200 installed. Had we actually damaged the transmission which does happen on some of the JD 4000 series due to the aluminum shift forks, the cost goes up more. That cost can easily exceed $2500 not including installation.
2. Loss of power to the ground
OK, this is true, no doubt. It's small, it may not be of any issue. I should think of more importance would be that in a heavy pulling situation like you would encounter when pulling a set of rippers through the ground hour on end, would be the heat generated by hydros and be a drawback. A manual would be probably be a better choice if this is what you do a considerable amount of.
3. Difficult to get constant speed #'s
As you and I have discussed before, about the only time this would be an issue would be when pulling a seeder or perhaps a sprayer. With my cruise control and digital speed readout, providing I'm not climbing a hill, the speed is dead on, cruise control is so easy to use. The gear will slow down going up a hill as well and will also need compensating. Farming applications may benefit from geared in this application but it's getting to be less of an issue.
4. More expensive to fix.
See durability. This is not necessarily true. Establishing a value here is difficult.
5. More expensive initially
A little bit. On a $20,000 tractor, expect about $1000 more then shuttle shift. The actual cost varies because dealers will work ther price to move more of what they have. In my area, HST is hardly more since it's the dominant transmission in stock.
6. Speed when using the loader
Bring em on baby. Lets see a JD 4410 with power reverser vs my L3830HST. No problem. Both work very well, I just know from experience, I'm faster on my HST.
7. One is not better then the other.
Absolutely, no question. I own both HST and a manual and use a shuttle quite a bit. They all have their benefits.
One thing about HST that is often overlooked by folks who don't use HST is their ability to instantly change speed. A real bonus on rough terrain. Their performance here is superb and for the most part, unmatched by any transmission I have used. They not only slow down immediately as your foot relaxes pressure, but the inherent design of HST brakes the tractor simultaneously as well as getting you to the new slower speed. I cannot tell you what a huge benefit this is when mowing areas less then smooth. On a manual, your choice is to lift off on the accelerator which will decrease speed but not nearly as responsively and in doing so, decreases the PTO speed. Other options include slipping the clutch or clutching and braking.
Rat...
